Deposition of boron and carbon containing materials

ABSTRACT

Methods of depositing boron and carbon containing films are provided. In some embodiments, methods of depositing B,C films with desirable properties, such as conformality and etch rate, are provided. One or more boron and/or carbon containing precursors can be decomposed on a substrate at a temperature of less than about 400° C. In some embodiments methods of depositing silicon nitride films comprising B and C are provided. A silicon nitride film can be deposited by a deposition process including an ALD cycle that forms SiN and a CVD cycle that contributes B and C to the growing film.

BACKGROUND

1. Field

The present disclosure relates generally to the field of semiconductordevice manufacturing and, more particularly, to deposition of boron andcarbon containing materials.

2. Description of the Related Art

Boron and carbon containing materials, such as boron and carbon films,can have a wide variety of uses, including uses in the semiconductorindustry. Silicon nitride based materials can be modified to includeboron and carbon components, for example forming silicon nitride filmscomprising boron and carbon components. Boron and carbon films andsilicon nitride films comprising boron and carbon components may havevarious applications in fabrication processes of semiconductor devices.

As the physical geometry of semiconductor devices shrinks, deposition offilms on three-dimensional structures having high aspect ratios isdesired. Therefore, deposition processes that provide films which candemonstrate conformal coverage of three-dimensional structures havinghigh aspect ratios are desired. Additionally, films are desired thatdemonstrate an advantageous etch selectivity with respect one or moreother materials in the semiconductor device, and/or a desirable etchrate in a dry etch and/or wet etch process.

SUMMARY

In some aspects, methods of forming silicon nitride films comprisingboron and carbon are provided. in some embodiments, methods ofdepositing a silicon nitride based film comprising boron and carbon on asubstrate in a reaction space can include contacting the substrate witha vapor-phase silicon reactant to form a layer of the reactant on asurface of the substrate; contacting the surface of the substratecomprising the silicon reactant with a nitrogen reactant; and contactingthe substrate with a vapor phase boron and/or carbon reactant. In someembodiments, at least one of contacting the substrate with a vapor-phasesilicon reactant, contacting the silicon reactant with a nitrogenprecursor, and contacting the substrate with a vapor phase boronreactant are performed two or more times.

Methods of depositing a silicon nitride thin film comprising boron andcarbon on a substrate in a reaction space can include exposing thesubstrate to a vapor-phase silicon precursor; removing excess siliconprecursor and reaction byproducts from the reaction space, for examplewith a purge gas and/or vacuum; contacting the remaining siliconreactant on the substrate surface with a nitrogen precursor; andexposing the substrate to a vapor-phase boron precursor. In someembodiments, at least one of exposing the substrate to a vapor-phasesilicon precursor, exposing the substrate to a purge gas and/or avacuum, contacting the adsorbed silicon reactant with a nitrogenprecursor, and exposing the substrate to a vapor-phase boron precursor,can be performed two or more times.

In some aspects, methods of forming boron carbon films are provided. insome embodiments, methods of depositing a boron and carbon film on asubstrate in a reaction space can include contacting the substrate witha vapor phase boron precursor at a process temperature of about 325° C.to about 400° C. to form the boron and carbon film on the substrate,where the vapor phase boron precursor decomposes on the substrate.

In some embodiments, methods of forming a boron and carbon film on asubstrate in a reaction space can include contacting a three-dimensionalstructure on the substrate with a vapor phase boron precursor at aprocess temperature of less than about 400° C. to form the boron andcarbon film on the three-dimensional structure, where the boron andcarbon film has a step coverage of greater than about 80%. In someembodiments, the methods can include purging the reaction spacesubsequent to contacting the three-dimensional structure on thesubstrate with the vapor phase boron precursor.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages are described herein.Of course, it is to be understood that not necessarily all such objectsor advantages need to be achieved in accordance with any particularembodiment. Thus, for example, those skilled in the art will recognizethat the invention may be embodied or carried out in a manner that canachieve or optimize one advantage or a group of advantages withoutnecessarily achieving other objects or advantages.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments will becomereadily apparent to those skilled in the art from the following detaileddescription having reference to the attached figures, the invention notbeing limited to any particular disclosed embodiment(s).

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure are described with reference to the drawings of certainembodiments, which are intended to illustrate certain embodiments andnot to limit the invention.

FIG. 1 shows a flow chart of an example of a process for depositing aboron and carbon film, according to an embodiment.

FIG. 2 shows a flow chart of another example of a process for depositinga boron and carbon film, according to an embodiment.

FIG. 3 is a graph of the growth rates of boron and carbon films versusprocess temperatures according to an embodiment.

FIG. 4 is a graph showing fourier transform infrared spectroscopy (FTIR)spectra of a boron and carbon film, deposited according to oneembodiment.

FIGS. 5A-5D are SEM images of a boron and carbon film deposited on ahigh aspect ratio trench structure.

FIG. 6 shows a flow chart of an example of a process for depositing asilicon nitride film comprising boron and carbon, according to anembodiment.

FIG. 7 shows a flow chart of an example of a process for depositing asilicon nitride film comprising boron and carbon, according to anotherembodiment.

FIG. 8A is a graph of compositions of examples of silicon nitride filmscomprising boron and carbon as a function of the percentage of TEBpulses in the deposition process.

FIG. 8B is a graph of film growth rates of examples of silicon nitridefilms comprising boron and carbon as a function of the percentage of TEBpulses in the deposition process.

FIG. 9 shows FTIR spectra of examples of silicon nitride filmscomprising boron and carbon.

FIG. 10 shows XRR data of examples of silicon nitride films comprisingboron and carbon deposited according to embodiments disclosed herein.

FIG. 11 is a graph of film etch rates of examples of silicon nitridefilms comprising boron and carbon as a function of the fraction of TEBpulses in the deposition process.

FIGS. 12A-12D are SEM images showing etch performance of an example of asilicon nitride film comprising boron and carbon.

FIGS. 13A-13D are SEM images showing etch performance of an example of asilicon nitride film comprising boron and carbon components.

FIGS. 14A-14D are SEM images showing step coverage of an example of asilicon nitride film comprising boron and carbon components.

DETAILED DESCRIPTION

Although certain embodiments and examples are described below, those ofskill in the art will appreciate that the invention extends beyond thespecifically disclosed embodiments and/or uses and obvious modificationsand equivalents thereof. Thus, it is intended that the scope of theinvention herein disclosed should not be limited by any particularembodiments described below.

Films comprising boron and carbon can have a variety of desirableproperties, including chemical stability, mechanical strength, andthermal and electrical properties. As a result, such films have diverseapplications in many technical fields, including applications in thesemiconductor, medical, military, space and nuclear industries. Forexample, boron carbon films are used as neutron detectors, in thefabrication of semiconductor devices, and in the fabrication ofmicroelectromechanical systems (MEMS). They may be used in tribologicalcoatings for MEMS components and/or as sacrificial films insemiconductor device fabrication processes. In some embodiments, boronand carbon-containing films can be used as an etch stop layer, as alayer for facilitating photolithography patterning processes, and/or asa doping layer (e.g., as a boron dopant source). Other uses outside ofthe semiconductor area will be apparent to the skilled artisan.

In some embodiments films comprised essentially of boron and carbonfilms are disclosed, along with methods for making such films, while inother embodiments films comprising boron and/or carbon as well as othercomponents are disclosed, along with methods for making such films. Forexample, in some embodiments silicon nitride films can be formed thatinclude boron and carbon components. Silicon nitride films comprisingboron and carbon can have a wide variety of applications, including insemiconductor devices. Silicon nitride films comprising boron and carboncomponents can form a part of semiconductor devices (e.g., FinFETs),and/or be a part of processes for fabricating semiconductor devices. Forexample, silicon nitride films comprising boron and carbon componentscan be deposited on three-dimensional (3-D) features duringsemiconductor device fabrication processes, for example as a spacermaterial for a transistor gate feature (e.g., as spacer material of gatefeatures in multi-gate transistors such as FinFETs), and/or as asacrificial layer in the semiconductor device fabrication process.

One or more processes described herein may be used to form boron carbonfilms and/or silicon nitride films comprising boron and carbon, wherethe films have one or more desirable characteristics, such as adesirable level of conformal coverage of three-dimensional features, adesirable dry etch rate, a desirable wet etch rate, and/or a desirableetch selectivity with respect to another material (e.g., a thermalsilicon oxide (TOX) layer in a semiconductor device). For example, filmsdeposited according to one or more processes described herein, such as aboron and carbon film or a silicon nitride film comprising boron andcarbon, can demonstrate improved step coverage, reduced etch rate in awet etchant (e.g., resistance against wet etchant, such as a dilutehydrofluoric acid (HF or dHF) solution, such as a 0.5 weight % HFsolution), and/or a reduced wet etch ratio with respect to a thermalsilicon oxide (TOX) material (e.g., to provide a ratio of a wet etchrate of the silicon nitride based film to a wet etch rate of the TOX ofless than about 1, including less than about 0.5) relative to similarfilms deposited by other methods. In some embodiments, a silicon nitridefilm including boron and carbon components can have a desirabledielectric constant (κ-value), for example suitable for use as a spacermaterial for a transistor gate feature. In some embodiments, a siliconnitride film including boron and carbon components can have a dielectricconstant of less than about 7, including between about 4.8 and about 7,and between about 4.8 and about 6, as discussed below.

Boron and Carbon Films

As described herein, films comprised primarily of boron and carbon (alsoreferred to boron carbon films, or B,C films, as discussed below) andformed according to one or more processes described herein canadvantageously demonstrate various desirable characteristics. In someembodiments, the boron and carbon films can advantageously demonstratedesirable levels of conformality when deposited on three-dimensional(3-D) features of a substrate, such as 3-D features having high aspectratios. For example, the boron and carbon films may have a conformalityof greater than about 90%, including greater than about 95%, whendeposited on features having aspect ratios of about 3:1 or higher,including about 10:1 or higher, about 20:1 or higher, about 25:1 orhigher, about 40:1 or higher, about 50:1 or higher, or about 80:1 orhigher. In some embodiments, the boron and carbon films have aconformality greater than about 90%, including greater than about 95%,when deposited on features having aspect ratios of about 20:1 orgreater, including about 40:1 or higher, and about 80:1 or greater.

In some embodiments, the boron and carbon films can demonstrate reducedwet etch rates. For example, the boron and carbon films can demonstratereduced wet etch rates in dilute hydrofluoric acid solutions (dHF)(e.g., an etch rate of less than about 0.3× that of TOX films exposed tothe dHF). In some embodiments, the boron and carbon films can havenegligible wet etch rates in dilute HF. In some embodiments, the boronand carbon films have a wet etch rate of less than about 0.2 nanometersper min (nm/min) in dilute HF, preferably less than about 0.1 nm/min,and more preferably less than about 0.05 nm/min. In some embodiments,the boron and carbon films can exhibit etch rates of less than about 0.2nm/min, preferably less than about 0.1 nm/min, and more preferably lessthan about 0.05 nm/min, in wet etchants comprising nitric acid (HNO₃)sodium hydroxide (NaOH), hydrochloric acid (HCl) sulfuric acid (H₂SO₄),and/or phosphoric acid (H₃PO₄). In some embodiments the wet etch rate isbelow the detection limit using one of the recited etchants.

In some embodiments, boron and carbon films formed according to one ormore processes described herein demonstrate desirable etch resistancewhile having a desirable film density, such as film densities of about2.0 to about 2.5 grams per cubic centimeter (g/cm³). For example, theboron and carbon films may have wet etch rates as described herein whilehaving film densities of about 2.0 g/cm³ to about 2.5 g/cm³.

In some embodiments, the boron and carbon films can demonstrate one ormore of these desirable characteristics prior to being subjected to apost-deposition treatment process, such as the post-deposition treatmentprocesses that are described in further detail herein. In someembodiments, a post-deposition treatment process further improves one ormore of these desirable characteristics.

In some embodiments, a boron and carbon film deposited on a surfacecomprising silicon (e.g., on a surface of a silicon based layer, such asa silicon layer, a silicon nitride layer, a silicate layer etc. . . . )can demonstrate increased uniformity and/or conformality, such ascompared to a boron and carbon film deposited on a surface of adifferent material (such as a material that does not comprise silicon).For example, a boron and carbon film deposited on a silicon nitride(SiN) surface (e.g., on a surface of a silicon nitride layer, forexample on a silicon nitride substrate) can demonstrate increaseduniformity. Without being limited by any particular theory or mode ofoperation, an improved interaction between the silicon-based surface andone or more components of the boron and carbon film may advantageouslyfacilitate the improved uniformity and/or conformality of the depositedfilm.

As discussed above, a boron and carbon film typically comprisesprimarily boron and carbon. The formula of a boron and carbon film isgenerally referred to herein as B,C for convenience and simplicity.However, the skilled artisan will understand that the actual formula ofa B,C film can be B_(x)C. In some embodiments, for example, x can varyfrom about 0.1 to about 25. In some cases, x preferably varies fromabout 1 to about 10, and more preferably from about 1 to about 2. Forexample, x can be about 1.5.

In some embodiments, a boron and carbon film is deposited on a substrateby a CVD process comprising decomposing one or more boron precursors(e.g., boron reactants) on a substrate surface at a temperature of lessthan about 400° C., and at a pressure of about 0.1 Torr to about 10Torr. In some embodiments, a boron precursor may comprise both boron andcarbon. Thus, in some embodiments a CVD process for depositing a boronand carbon film may include decomposition of a single boron precursorcomprising both boron and carbon. In some embodiments, a CVD processcomprises decomposing two or more precursors on the substrate surface toform the boron and carbon film. In some embodiments, at least one of thetwo or more precursors comprises boron (B). In some embodiments, atleast one of the two or more precursors comprises carbon (C).

In some embodiments, no or substantially no plasma is used in thedeposition of the boron and carbon films (e.g., no or substantially noplasma is used for boron and carbon film growth). In some embodiments, aCVD process may be a pulsed thermal CVD process in which multiple pulsesof a single boron precursor are provided to deposit a film of desiredthickness. In some embodiments, a single, pulse of the boron precursoris provided to deposit a film of the desired thickness. A thermal CVDprocess may comprise no plasma or substantially no plasma in thedecomposition of precursors. In some embodiments, a purge step may beperformed between boron precursor pulses, for example to remove excessreactant and/or reaction byproducts from the reaction space. In someembodiments the substrate may be moved to a space in which it is notexposed to the precursor. In some embodiments, a boron precursor pulsecan comprise one or more carrier gases, such as nitrogen gas, heliumgas, neon gas, and/or xenon gas. In some embodiments, the boronprecursor pulse comprises a mixture of two or more carrier gases. Insome embodiments, a mixture of two or more carrier gases comprises argongas and/or hydrogen gas. For example, a mixture of two or more carriergases can comprise two or more gases selected from nitrogen gas, heliumgas, neon gas, xenon gas, argon gas, and hydrogen gas.

FIG. 1 shows a flow chart 100 illustrating a process for forming a boronand carbon (B,C) film. In block 102, a substrate is exposed to one ormore vapor phase boron reactants (e.g., boron and/or carbon precursors).A carrier gas may be used to transport the one or more vapor phase boronreactants to the substrate. In some embodiments the carrier gas mayfacilitate one or more interactions between reactants and/or betweenreactants and the substrate surface for forming the boron and carbonfilm, while not or substantially not contributing to growth of the boronand carbon film.

In some embodiments, the substrate is exposed to a single vapor phaseboron reactant. In some embodiments, the single vapor phase boronreactant comprises both boron (B) and carbon (C). In some embodiments,the substrate is exposed to two or more vapor phase boron reactants. Forexample, at least one of the two or more vapor phase boron reactantscomprises carbon (C). In some embodiments, at least one of the two ormore vapor phase boron reactants comprises boron (B).

In some embodiments, the carrier gas can comprise an inert carrier gas,such as nitrogen gas (N₂), helium (He), xenon (Xe) and/or neon (Ne). Insome embodiments, the carrier gas can comprise a mixture of two or moregases, including two or more gases selected from nitrogen gas, heliumgas, neon gas, xenon gas, argon gas, and hydrogen gas. In block 104,exposure of the substrate to the carrier gas and the one or more vaporphase boron reactants can be repeated a number of times, such as in apulsed CVD process. For example, the substrate can be exposed to thecarrier gas and the one or more boron carbon vapor phase reactants for afirst duration of time, and the exposure may be repeated about 5 timesto about 5,000 times, including about 100 times to about 3,000 times,including about 1000 times, and about 2,000 times. The duration of timemay be the same in each of the repetitions, or cycles, or may varybetween one or more cycles. The number of repetitions can be selected tofacilitate deposition of a boron and carbon film of a desired thickness,for example. In some embodiments, an exposure of the substrate to thecarrier gas and the one or more vapor phase boron reactants may befollowed by discontinuing flow of the one or more vapor phase boronreactants into the reaction space. In some embodiments, an exposure ofthe substrate to the carrier gas and the one or more vapor phase boronreactants can be followed by a purge step and/or transport of thesubstrate to a space away from the reactants (e.g., such that thesubstrate is not or substantially not exposed to the reactants). Thepurge step may be configured to remove one or more excess reactantsand/or reaction byproducts from the reactor chamber. In someembodiments, a purge step and/or transport of the substrate follows eachexposure of the substrate to the carrier gas and the one or more vaporphase boron reactants. For example, subsequent to each exposure of thesubstrate to the reactant(s) in each cycle, the substrate may be movedto a space free or substantially free of the reactants, or the reactormay be purged of excess reactants and/or reaction byproducts. In someembodiments, the purge step comprises continuing flow of the carrier gas(e.g., continuing flow of the carrier gas, such as at least onecomponent of a multi-component carrier gas, at a same or different flowrate as compared to that during the reactant pulse). For example, aprocess 100 for depositing boron and carbon films may includecontinuously flowing the carrier gas while periodically flowing the oneor more vapor phase boron reactants.

In some embodiments a process for depositing a boron and carbon (B,C)film may include a chemical vapor deposition (CVD) process. Referring toFIG. 1, in some embodiments the process 100 includes a thermal CVDprocess performed at reduced process temperatures, for exampletemperatures less than about 400° C. A thermal CVD process can be aprocess in which no or substantially no plasma is applied, such as forfacilitating decomposition of precursors used to deposit the film. Theprocess temperature as referred to herein can comprise a temperature ofa reactor chamber susceptor, a reactor chamber wall, and/or atemperature of the substrate itself. For example, in some embodimentsthe process 100 for depositing the boron and carbon film can beperformed with a process temperature of up to about 400° C. In someembodiments, the process 100 for depositing the boron and carbon filmcan be performed with a process temperature of about 325° C. to about400° C., preferably about 350° C. to about 400° C., and most preferablyabout 375° C. to about 400° C. Without being limited by any particulartheory or mode of operation, deposition of boron and carbon films attemperatures less than about 400° C. may advantageously facilitatedeposition in a surface reaction limited regime, facilitating formationof boron and carbon films having one or more desirable characteristicsdescribed herein (e.g., increased conformality performance and/ordecreased etch rate).

In some embodiments, deposition of boron and carbon films (B,C) can beperformed at process temperatures of about 400° C. to about 450° C.,including for example, about 400° C. to about 425° C.

According to some embodiments of the present disclosure, the pressure ofthe reactor chamber during processing is maintained at about 0.01 Torrto about 50 Torr, preferably from about 0.1 Torr to about 10 Torr. Insome embodiments, deposition of boron and carbon films can be performedwith a reactor chamber pressure of about 0.5 Torr to about 3 Torr. Theselected reaction chamber pressure may serve to facilitate formation ofboron and carbon films having desired conformality and/or etch rateperformances.

As described herein, a carrier gas may comprise an inert carrier gas,such as nitrogen gas (N₂), helium (He), xenon (Xe) and/or neon (Ne). Forexample, block 102 of FIG. 1 may include exposing a substrate to one ormore boron reactants and nitrogen gas. Without being limited by anyparticular theory or mode of operation, nitrogen gas, helium, xenon, andneon can exhibit an increased thermal conductivity (e.g., for example agreater thermal conductivity as compared to that of other inert carriergases, such as argon (Ar)), thereby facilitating decomposition of theone or more boron and/or carbon precursors. Further, without beinglimited by any particular theory or mode of operation, a carrier gashaving an increased thermal conductivity may facilitate decomposition ofthe one or more boron and/or carbon precursors in high aspect ratiofeatures of a 3-D substrate surface, facilitating formation of aconformal and/or etch resistant boron and carbon film over the highaspect ratio features. For example, use of carrier gas comprisingnitrogen gas, helium, xenon, and/or neon, including carrier gas mixturescomprising two or more of nitrogen gas, helium, xenon, neon, argonand/or hydrogen, may facilitate formation of a conformal and/or etchresistant boron and carbon film.

In some embodiments, a process 100 for depositing the boron and carbon(B,C) film comprises a pulsed thermal CVD process. For example, theprocess 100 may comprise contacting the substrate with a reactant for adesired amount of time, such as by supplying into the reactor chamber areactant pulse for a desired duration. The reactant pulse may comprise acarrier gas (e.g., nitrogen gas, helium and/or neon) and one or moreboron reactants. In some embodiments, the reactant pulse is repeated anumber of times to deposit a boron and carbon film of desired thicknessand/or composition. In some embodiments one or more reactant pulse canbe followed by a purge step and/or transport of the substrate into aspace free or substantially free of the reactants. For example, thesubstrate may first be transported to a space free or substantially freeof the reactants and the reactor chamber may then be purged of anyexcess reactants and/or reaction byproducts. For example, each reactantpulse of a plurality of reactant pulses may be followed by a purge stepand/or transport of the substrate to a space free or substantially freeof the reactants. The purge step may be configured to remove one or moreexcess reactants and/or reaction byproducts from the reactor chamber.For example, a purge step may comprise flowing one or more purge gasesthrough the reactor chamber, and/or evacuating the reactor chamber toremove or substantially remove excess reactants and/or reactionbyproducts (e.g., by drawing a vacuum upon the reactor chamber). In someembodiments, the purge gas comprises an inert gas. In some embodiments,the purge gas comprises nitrogen gas. In some embodiments, the purge gascomprises a noble gas.

In some embodiments, a reactant pulse can be followed by discontinuingflow of the one or more vapor phase boron reactants into the reactorchamber while continuing flow of the carrier gas. For example, a purgestep may comprise continued flow of the carrier gas (e.g., at a same ordifferent flow rate, such as a higher flow rate, as compared to thatduring the reactant pulse) for purging the reactor chamber. For example,a purge step may comprise continuing flow of at least one component of acarrier gas comprising a mixture of two or more gases for purging thereactor chamber. In some embodiments, a process 100 for depositing boronand carbon films may include continuously flowing the carrier gas whilealternating flow of the one or more vapor phase boron reactants.

A duration of the reactant pulse can be selected to provide a desiredquantity of the one or more boron reactants into the reactor chamber. Insome embodiments, a reactant pulse can have a duration of about 0.1seconds (s) to about 5 s, including about 0.1 s to about 1 s. Forexample, a reactant pulse can have a duration of about 0.5 s. In someembodiments, an interval between reactant pulses can be about 1 s toabout 15 s. In some embodiments, the interval comprises a purge step forpurging excess reactants and/or reaction byproducts from the reactorchamber. In some embodiments, the interval comprises transport of thesubstrate to a space free or substantially free of reactants. Forexample, the interval may comprise transport of the substrate to a spacefree or substantially free of reactants, and a purge step having aduration of about 1 s to about 15 s, including about 1 s to about 10 s.For example, the purge step can have a duration of about 5 s.

In some embodiments, a duration of the reactant pulse and/or theinterval between reactant pulses (e.g., including for example, durationof a purge step) can be selected based a surface area of the substrateon which the boron and carbon film is deposited, an aspect ratio of athree dimensional (3-D) structure on which the boron and carbon film isdeposited, and/or a configuration of the reactor chamber. For example,the reactant pulse and/or the interval between reactant pulses may havean increased duration for depositing a boron and carbon film on a largersurface area, 3-D structures having increased aspect ratios, and/or fordeposition in a batch reactor. In some embodiments, an increasedreactant pulse duration and/or interval between reactant pulses isselected for deposition on ultra-high aspect ratio features, includingfor example, features having aspect ratios of about 40:1 and greater,including about 80:1 and greater.

In some embodiments, the one or more boron reactants are supplied intothe reactor chamber from a respective source container in which thereactants are stored in vapor form. Vapor pressure of each reactant canfacilitate delivery of the reactant into the reactor chamber. Forexample, the vaporized reactants can be provided into the reactorchamber using a vapor draw technique. In some embodiments, a sourcecontainer can be maintained at a temperature of about 20° C. to about25° C. A mass flow rate of a vaporized reactant into the reactor chambermay be controlled, for example, by controlling the extent to which asupply valve for providing the vaporized reactant into the reactorchamber is kept open.

In some embodiments, a suitable boron reactant may include one or morecompounds comprising a B—C bond. In some embodiments, a suitable boronreactant can include a boron compound having at least one organicligand. In some embodiments, the organic ligand can have double and/ortriple bonds. In some embodiments, the organic ligand can be a cyclicligand. In some embodiments, the organic ligand can comprise delocalizedelectrons. In some embodiments, a suitable boron reactant can includetrialkylboron compounds. In some embodiments, a suitable boron reactantcan include triethylboron (B(C₂H₅)₃, TEB). In some embodiments, asuitable boron reactant can include trimethylboron (B(CH₃)₃, TMB). Insome embodiments, a suitable boron reactant can include trialkylboroncompounds having linear or branched alkyl groups, including for examplelinear or branched C3-C8, and more preferably including linear orbranched C3-C5. Suitable boron reactants can include a variety of otherboron-containing reactants. In some embodiments, a boron reactant caninclude a boron halide, an alkylboron, and/or a borane. In someembodiments, a boron reactant can include boron halides, borane halidesand complexes thereof. For example, a suitable boron halide can have aboron to halide ratio of about 0.5 to about 1.

Suitable boranes can include compounds according to formula I or formulaII.B_(n)H_(n+x)  (formula I)

Wherein n is an integer from 1 to 10, preferably from 2 to 6, and x isan even integer, preferably 4, 6 or 8.B_(n)H_(m)  (formula II)

Wherein n is an integer from 1 to 10, preferably form 2 to 6, and m isan integer different than n, from 1 to 10, preferably from 2 to 6.

Of the above boranes according to formula I, examples includenido-boranes (B_(n)H_(n+4)), arachno-boranes (B_(n)H_(n+6)) andhyph-boranes (B_(n)H_(n+8)). Of the boranes according to formula II,examples include conjuncto-boranes (B_(n)H_(m)). Also, borane complexessuch as (CH₃CH₂)₃N—BH₃ can be used.

In some embodiments, suitable boron reactants can include boranehalides, particularly fluorides, bromides and chlorides. An example of asuitable compound is B₂H₅Br. Further examples comprise boron halideswith a high boron/halide ratio, such as B₂F₄, B₂C₁₄ and B₂Br₄. It isalso possible to use borane halide complexes.

In some embodiments, halogenoboranes according to formula III can besuitable boron reactants.B_(n)X_(n)  (formula III)

Wherein X is Cl or Br and n is 4 or an integer from 8 to 12 when X isCl, or n is an integer from 7 to 10 when X is Br.

In some embodiments, carboranes according to formula IV can be suitableboron reactants.C₂B_(n)H_(n+x)  (formula IV)

Examples of carboranes according to formula IV include closo-carboranes(C2B_(n)H_(n+2)), nido-carboranes (C₂B_(n)H_(n+4)) andarachno-carboranes (C₂B_(n)H_(n+6)).

In some embodiments, amine-borane adducts according to formula V can besuitable boron reactants.R₃NBX₃  (formula V)

Wherein R is linear or branched C1 to C10, preferably C1 to C4 alkyl orH, and X is linear or branched C1 to C10, preferably C1 to C4 alkyl, Hor halogen.

In some embodiments, aminoboranes where one or more of the substituentson B is an amino group according to formula VI can be suitable boronreactants.R₂N  (formula VI)

Wherein R is linear or branched C1 to C10, preferably C1 to C4 alkyl orsubstituted or unsubstituted aryl group.

An example of a suitable aminoborane is (CH₃)₂NB(CH₃)₂.

In some embodiments, a suitable boron reactant can include a cyclicborazine (—BH—NH—)₃ and/or its volatile derivatives.

In some embodiments, alkyl borons or alkyl boranes can be suitable boronreactants, wherein the alkyl is typically linear or branched C1 to C10alkyl, preferably C2 to C4 alkyl.

According to some embodiments, a process for depositing a boron andcarbon (B,C) film comprises a pulsed thermal CVD process performed at aprocess temperature of about 375° C. to about 400° C., and at a pressureof about 0.5 Torr to about 3 Torr. The process may include contactingthe substrate with a reactant pulse comprising nitrogen gas as thecarrier gas and triethylboron (TEB) as the boron and carbon reactant.The supply of TEB may be drawn from a source container for storing TEBat a temperature of about 20° C. to about 25° C. (e.g., a needle valvefor providing TEB flow into the reactor chamber may be kept open atabout two turns). The reactant pulse may have a duration of about 0.5 s.In some embodiments a single cycle of the process may include thereactant pulse followed by a period of time in which the substrate isnot exposed to the reactant, such as a purge step. The purge step maycomprise flowing nitrogen gas without the reactant, for example for aduration of about 5 s. The process may include repeating the cyclecomprising the reactant pulse followed by the purge step a number oftimes to achieve a boron and carbon film of a desired thickness and/orcomposition. For example, the cycle may be repeated up to about 1,000times, about 1,500 times, about 2,000 times, or about 5,000. In someembodiments, the cycle can be repeated about 2 to about 1,000 times,including about 2 to about 2,000 times, about 3 to about 2,000 times, orabout 5 to about 5,000 times. In the cycle can be repeated from about 10to about 100 times. In some embodiments, the cycle can be repeated about50 to about 2,000 times. In some embodiments, the cycle can be repeatedabout 100 to about 1,500 times.

One or more boron and carbon (B,C) films formed according to one or moreprocesses described herein may advantageously demonstrate desiredconformality, such as when deposited on high aspect ratio features of3-D substrate surfaces, and/or desired etch rate performances (e.g., wetetch rate performance, such as wet etch rate performance in dilute HFsolution). The films may also exhibit a reduced film density, such asfilm densities of about 2.0 grams per cubic centimeter (g/cm³) to about2.5 g/cm³. In some embodiments, the boron and carbon films candemonstrate a conformality of greater than about 80%, preferably greaterthan about 90% and more preferably greater than about 95%, for examplewhen the boron and carbon films are formed on 3-D structures havingaspect ratios of about 3:1 or higher, including about 10:1 or higher,about 25:1 or higher, or about 50:1 or higher. In some embodiments, theboron and carbon films can demonstrate a conformality of greater thanabout 80%, preferably greater than about 90% and more preferably greaterthan about 95%, when the boron and carbon films are formed on 3-Dstructures having aspect ratios of about 20:1 or greater, about 40:1 orgreater, or about 80:1 or greater. For example, one or more boron andcarbon films formed according to one or more processes described hereinmay demonstrate a conformality performance of greater than about 95%when deposited on high aspect ratio features of a 3-D substrate surface,including aspect ratios of up to about 250:1, including about 150:1 andabout 100:1.

As described herein, a boron and carbon (B,C) film can be used in someembodiments as a sacrificial film in a semiconductor device fabricationprocess. For example, the boron and carbon film may be selectivelyremoved in an etch process. In some embodiments, a boron and carbon filmmay form a part of a finished semiconductor device. For example, theboron and carbon film may be more resistant to etch than one or moreother materials used in the fabrication of the semiconductor device. Insome embodiments, the boron and carbon film may be etched by a dry etchprocess and/or a wet etch process. In some embodiments, a sacrificialboron and carbon film can be selectively removed during fabrication of asemiconductor device using an etch process comprising chlorine (Cl)and/or fluorine (F), such as chlorine and/or fluorine containing plasmaprocesses. In some embodiments, the boron and carbon films can be moreresistant to one or more etchants, including wet etchants such as diluteHF solutions.

In some embodiments, the boron and carbon film can demonstrate a desiredwet etch selectivity, such as a wet etch selectivity with respect to athermal silicon oxide (TOX) layer. For example, the boron an carbon filmmay be more resistant to wet etch than the thermal silicon oxide layer,having a ratio of a wet etch rate of the boron an carbon film to a wetetch rate of a thermal silicon oxide layer less than about 1 (e.g., indilute HF solution), less than about 0.5, or less than about 0.3. Insome embodiments, the ratio of a wet etch rate of the boron and carbonfilm to a wet etch rate of the thermal silicon oxide layer can be lessthan about 0.1. In some embodiments, the ratio of a wet etch rate of theboron and carbon film to a wet etch rate of the thermal silicon oxidelayer can be less than about 0.05.

In some embodiments, the boron and carbon film can advantageouslydemonstrate desirable wet etch rates, including etch rates in dilute HFsolution. For example, the boron and carbon film can advantageouslydemonstrate etch rates of less than about 0.2 nanometers per minute(nm/min), including preferably less than about 0.1 nm/min, morepreferably less than about 0.05 nm/min, and most preferably less thanabout 0.02 nm/min.

In some embodiments, the boron and carbon film can demonstrate wet etchrates of less than about 0.2 nm/min, including preferably less thanabout 0.1 nm/min, more preferably less than about 0.05 nm/min, and mostpreferably less than about 0.02 nm/min in the following wet etchantsolutions and at the specified temperatures: phosphoric acid (H₃PO₄)solution at a concentration of about 85 weight % at about roomtemperature (e.g., a temperature of about 25° C.), a concentrated nitricacid HNO₃ solution (e.g., a solution having a HNO₃ concentration ofabout 65 to about 75 weight %) at about 80° C., a 5.5 weight %hydrofluoric acid (HF) at about room temperature (e.g., a temperature ofabout 25° C.), a solution having a ratio of nitric acid:hydrofluoricacid:water (HNO₃:HF:H₂O) at about 1:1:5 at about room temperature (e.g.,a temperature of about 25° C.), an aqueous solution of sodium hydroxide(NaOH) having a concentration of NaOH of about 10 weight % at about roomtemperature (e.g., a temperature of about 25° C.), a concentratedhydrochloric acid (HCl) solution (e.g., a solution having an HClconcentration of about 35 to about 40 weight %) at about roomtemperature (e.g., a temperature of about 25° C.), and a concentratedsulfuric acid solution (H₂SO₄) (e.g., a solution have a H₂SO₄concentration of greater than about 90 weight %) at about roomtemperature (e.g., a temperature of about 25° C.).

In some embodiments, the boron and carbon film may be selectivelyremoved. In some embodiments, the boron and carbon film can have a etchselectivity (e.g., a dry etch and/or a wet etch selectivity) withrespect to another material, such as a film of a different composition,in the device of about 5 or greater, including a selectivity of about 10or greater, about 20 or greater, or about 50 or greater.

In some embodiments, a portion of a boron and carbon film deposited on asidewall of a three-dimensional structure can demonstrate a desired etchrate, for example, as compared to an etch rate of a portion of the filmdeposited on a top surface of the three-dimensional feature. In someembodiments, a portion of a boron and carbon film deposited on asidewall of a three-dimensional structure can demonstrate a uniform orsubstantially uniform etch rate as a portion of the boron and carbonfilm deposited on a top surface of the structure. For example, a ratioof an etch rate of a sidewall portion of the boron and carbon film to anetch rate of a top surface portion of the boron and carbon film can beless than about 4, including less than about 2, about 1.5. In someembodiments, the ratio is about 1. In some embodiments, a uniformity ofa top surface portion and a sidewall portion of the boron and carbonfilm can be maintained after being exposed to one or more plasmaprocesses, such as a plasma post-deposition treatment process asdescribed herein.

One or more process parameters for boron and carbon (B,C) film growthprocess may be adjusted to achieve a desired boron and carbon filmcharacteristic. For example, selection of a boron reactant, a durationof a reactant pulse, a duration of a purge step, a process temperature,and/or a number of repetitions of the reactant pulse, may be determinedto provide a boron and carbon film comprising desirable characteristics.In some embodiments, one or more parameters of one cycle of a reactantpulse and purge step can be different from that of another cycle (e.g.,one cycle of the reactant pulse and purge step as described withreference to FIG. 1). In some embodiments, a boron reactant can have aB—C bond. In some embodiments, a boron reactant comprises at least oneorganic ligand, such as a hydrocarbon ligand, including a boron reactantcomprising an alkyl group.

FIG. 2 shows a flow chart 200 of another example of a process forforming boron and carbon (B,C) films, according to some embodiments. Inblock 202, the substrate is exposed to a boron and carbon film growthprocess. The boron and carbon film growth process may comprise adeposition process, such as a pulsed thermal CVD process, for depositinga boron and carbon film of a desired thickness and/or composition. Forexample, the boron and carbon film growth process may comprise repeatinga number of times a cycle comprising a reactant pulse followed by apurge step (e.g., the reactant pulse and purge step as described withreference to FIG. 1). The cycle may be repeated a number of times toachieve a desired boron and carbon film thickness and/or composition.

In block 204, a post-deposition treatment process can be carried out onthe deposited boron and carbon film. In some embodiments, thepost-deposition treatment process comprises a plasma process. Forexample, the treatment process may comprise contacting the depositedboron and carbon film with one or more energized species for a durationof time. In some embodiments, the post-deposition treatment processcomprises contacting the substrate comprising the boron and carbon filmwith a plasma. For example, the substrate can be contacted with a plasmagenerated using nitrogen-containing compounds (e.g., nitrogen gas), anoble gas, and/or oxygen-containing compounds (e.g., oxygen gas and/orozone). In some embodiments, the post-deposition treatment process canbe followed by a purge step. For example, the purge step may includeflow of nitrogen gas and/or one or more noble gases. In someembodiments, purging the reactor chamber subsequent to thepost-deposition treatment process can include turning off the plasmapower while continuing to flow one or more of the gases used to generatethe plasma for the post-deposition treatment process. For example,during the purge step the one or more gases used in generating theplasma for the post-deposition treatment process may continue to beflowed into the reactor while the plasma power is turned off, the flowrate of the one or more gases during the purge step being the same as ordifferent from that during the post-deposition treatment process.

In some embodiments, exposing a boron and carbon film to apost-deposition treatment process can facilitate a further reduced etchrate of the treated boron and carbon film, for example as compared tothat of a boron and carbon film formed without performing thepost-deposition treatment process. Without being limited by anyparticular theory or mode of operation, exposing a boron and carbon filmto a post-deposition treatment process as described herein may increasethe density of the boron and carbon film, thereby providing a treatedboron and carbon film exhibiting decreased etch rate as compared to anuntreated boron and carbon film. In some embodiments, the etch rate of aportion of the boron and carbon film deposited on a sidewall of athree-dimensional structure can demonstrate a uniform or substantiallyuniform etch rate as a portion of the boron and carbon film deposited ona top surface of the structure subsequent to exposure of the boron andcarbon film to a post-deposition treatment process (e.g., etch rateuniformity between a top portion and a sidewall portion of the boron andcarbon film can be maintained subsequent to exposure to a plasma processof the post-deposition treatment process, such as compared to that ofthe film prior to the post-deposition treatment process). For example, aratio of an etch rate of a sidewall portion of the boron and carbon filmto an etch rate of a top surface portion of the boron and carbon filmsubsequent to a post-deposition treatment process can be less than about4, including less than about 2, about 1.5. In some embodiments, theratio is about 1.

As described herein, in some embodiments, a post-deposition treatmentprocess may comprise contacting a deposited boron and carbon film with anitrogen-containing plasma (e.g., contacting the deposited boron andcarbon film with nitrogen-containing radicals and/or ions). One or morenitrogen-containing compounds may be used to generate thenitrogen-containing plasma, such as nitrogen-containing compounds whichdo not have hydrogen (H). For example, the post-deposition treatmentprocess may comprise energetic species generated using nitrogen gas(N₂).

In some embodiments, the post-deposition treatment process comprisesexposing the boron and carbon film to the nitrogen-containing plasma fora duration of about 1 to about 500 seconds (s), 10 s to about 300 s,including about 10 s to about 100 s, or about 10 s to about 50 s. Thenitrogen-containing plasma post-deposition treatment process may beperformed at a process temperature of about 100° C. to about 500° C.,including about 200° C. to about 500° C., and about 200° C. to about400° C., and a pressure of about 0.1 Torr to about 20 Torr, includingabout 1 Torr to about 10 Torr, and about 1 Torr to about 8 Torr. In someembodiments, a plasma power for generating the nitrogen-containingplasma can be about 50 Watts (W) to about 2000 W, including about 50 Wto about 1000 W, about 100 W to about 400 W, and about 200 W to about400 W.

In some embodiments, a post-deposition treatment process comprisescontacting a deposited boron and carbon film with a noble gas-containingplasma (e.g., contacting the deposited boron and carbon film with noblegas-containing radicals and/or ions). For example, the post-depositiontreatment process may comprise a plasma comprising energetic speciesgenerated using helium (He) gas, argon gas (Ar) and/or neon (Ne) gas. Insome embodiments, the post-deposition treatment process comprisesexposing the boron and carbon film to the noble gas-containing plasmafor a duration of about 10 seconds (s) to about 300 s, including about10 s to about 100 s. The noble gas-containing plasma post-depositiontreatment process may be performed at a process temperature of about100° C. to about 500° C., including about 200° C. to about 500° C., andabout 200° C. to about 400° C., and a pressure of about 0.1 Torr toabout 20 Torr, including about 1 Torr to about 10 Torr, and about 1 Torrto about 8 Torr. In some embodiments, a plasma power for generating thenoble gas-containing plasma can be about 50 Watts (W) to about 2000 W,including about 50 W to about 1000 W, about 100 W to about 400 W, andabout 200 W to about 400 W.

In some embodiments, the post-deposition treatment process comprisescontacting a deposited boron and carbon film with an oxygen-containing(O) plasma (e.g., contacting the deposited boron and carbon film withoxygen-containing radicals and/or ions). In some embodiments, theoxygen-containing plasma can be generated using oxygen-containingcompounds, such as oxygen gas (O₂) and/or ozone (O₃). In someembodiments, the post-deposition treatment process may comprise exposingthe boron and carbon film to the oxygen-containing plasma for a durationof about 10 seconds (s) to about 300 s, including about 10 s to about100 s. The oxygen-containing plasma post-deposition treatment processmay be performed at a process temperature of about 100° C. to about 500°C., including about 200° C. to about 500° C., and about 200° C. to about400° C., and a pressure of about 0.1 Torr to about 20 Torr, includingabout 1 Torr to about 10 Torr, and about 1 Torr to about 8 Torr. In someembodiments, a plasma power for generating the oxygen-containing plasmacan be about 50 Watts (W) to about 2000 W, including about 50 W to about1000 W, about 100 W to about 400 W, and about 200 W to about 400 W.

In some embodiments, the oxygen-containing plasma (e.g., generated usingoxygen gas and/or ozone) post-deposition treatment process can increasea refractive index of the boron and carbon film. In some embodiments,the oxygen-containing plasma post-deposition treatment process canreduce a thickness of the boron and carbon film (e.g., a thickness ofthe treated film can be less than a thickness of the film prior to beingexposed to the post-deposition treatment process). Without being limitedby any particular theory or mode of operation, exposing a boron andcarbon film to an oxygen-containing plasma may facilitate replacement ofhydrogen (H) and/or carbon (C) components of the film with oxygen (O),for example generating a BO_(x) containing film. Further without beinglimited by any particular theory or mode of operation, a change incomposition of the boron and carbon film, such as the replacement ofhydrogen (H) and/or carbon (C) components of the film with oxygen (O),may be reflected by a decrease in a refractive index of the film, and/ora decrease in film thickness (e.g., due to an increased film densityand/or removal of volatile BO_(x) species). For example, exposure of theboron and carbon film to an oxygen-containing plasma under certainconditions may result in complete or substantially complete removal ofthe deposited boron and carbon film (e.g., a plasma etch of the boronand carbon film).

In some embodiments, a post-deposition treatment process can beperformed once subsequent to depositing a boron and carbon film of adesired thickness and/or composition. In some embodiments, apost-deposition treatment process can be carried out at intervals afterevery repetition of a number of cycles of a deposition process fordepositing the boron and carbon film (e.g., after a number ofrepetitions of a cycle of the reactant pulse and purge step as describedwith reference to FIG. 1). For example, a post-deposition treatmentprocess may be performed after every 1, 2, 5, 10, 100, 1,000 cycles of aboron and carbon film deposition process. Other numbers of cycles mayalso be suitable. In some embodiments, a ratio of a number of cycles ofa process for depositing a boron and carbon film (e.g., a ratio of Y:X)to a number of cycles of the post-deposition treatment process forforming a boron and carbon film having desired characteristics can beabout 5,000:1 to about 1:1, including about 2,000:1 to about 50:1. Insome embodiments, the ratio of the number of cycles for the process ofdepositing a boron and carbon film to the number of cycles of thepost-deposition treatment process can be about 1,500:1 to about 1:1,including about 1,000:1 to about 1:1, about 500:1 to about 1:1, about100:1 to about 1:1, about 50:1 to about 1:1, and about 20:1 to about1:1.

In some embodiments, one or more parameters of the post-depositiontreatment process may be adjusted to facilitate formation of a boron andcarbon film having desirable characteristics. For example, a duration,plasma power, pressure, plasma composition and/or the number ofrepetitions of the process, may be selected to facilitate producing aboron and carbon film having desired etch characteristics.

A suitable reaction chamber for one or more boron and carbon (B,C) filmdeposition processes described herein may be part of a cluster tool inwhich a variety of different processes in the formation of an integratedcircuit are carried out. In some embodiments, one or more boron andcarbon film deposition processes described herein can be performed in abatch reactor, including for example in a mini-batch reactor (e.g., areactor having a capacity of eight substrates or less) and/or a furnacebatch reactor (e.g., a reactor having a capacitor of fifty or moresubstrates). In some embodiments, one or more boron and carbon filmdeposition processes described herein can be performed in a single waferreactor. In some embodiments, a spatial reactor chamber may be suitable.In some embodiments, a reactor chamber having a cross-flow configurationcan be suitable (e.g., a reactor chamber configured to provide gas flowparallel or substantially parallel to a substrate surface positioned inthe reactor chamber). In some embodiments, a reactor chamber having ashowerhead configuration can be suitable (e.g., a reactor chamberconfigured to provide gas flow perpendicular or substantiallyperpendicular to a substrate surface positioned in the reactor chamber).

Exemplary single wafer reactors are commercially available from ASMAmerica, Inc. (Phoenix, Ariz.) under the tradenames Pulsar® 2000 andPulsar® 3000 and ASM Japan K.K (Tokyo, Japan) under the tradename Eagle®XP and XP8. Exemplary batch ALD reactors are commercially available fromand ASM Europe B.V (Almere, Netherlands) under the tradenames A400™ andA412™.

Examples of B,C Films

FIG. 3 is a graph of the growth rates of boron and carbon (B,C) filmsdeposited according to some embodiments, in angstroms per cycle(Å/cycle), versus process temperature, in degrees Celsius. The boron andcarbon films (B,C) of FIG. 3 were deposited using a pulsed thermal CVDprocess in a Pulsar® 3000 reactor chamber having a cross-flowconfiguration. One cycle of the pulsed thermal CVD process included areactant pulse having a duration of about 0.5 s followed by a purge stephaving a duration of about 5 s. The reactant pulse included supplyingTEB and nitrogen gas into the reactor chamber. The TEB was supplied intothe reactor chamber using a vapor draw method by providing vaporized TEBfrom a source container maintained at a temperature of about 20° C. Thepressure of the reactor chamber during the reactant pulse was maintainedat about 0.1 Torr to about 10 Torr. The purge step included flowing ofnitrogen gas through the reactor chamber. Growth rates of boron andcarbon films deposited according to the pulsed thermal CVD process weremeasured at process temperatures of about 375° C., about 400° C. andabout 450° C. As shown in FIG. 3, the growth rate of the boron andcarbon film per cycle increased with increasing process temperature. Asshown in FIG. 3, a boron and carbon film deposited using such a pulsedthermal CVD process can have a linear or substantially linearrelationship with the process temperature.

Composition of boron and carbon (B,C) films deposited according to theprocess described with reference to FIG. 3 at a process temperature ofabout 400° C. was measured by rutherford backscattering spectrometry(RBS), and was found to have a boron and carbon stoichiometry of aboutB_(0.608)C_(0.392), or B_(1.5)C. The refractive index of boron andcarbon films deposited according to the process described with referenceto FIG. 3 at a process temperature of about 400° C. was measured byspectroscopic ellipsometry. The refractive index was found to be about1.98 at a wavelength of about 633 nanometers (nm). Wet etch rateperformance in dilute hydrofluoric acid solution (e.g., 0.5 weight %aqueous HF solution) of films deposited according to the processdescribed with reference to FIG. 3 at a process temperature of about400° C. were measured and was found to be surprisingly resistant to thedilute HF solution. It was found that the wet etch rate in dilute HFsolution was negligible, for example after up to about 10 minutesexposure to the dilute HF solution (e.g., a dHF dip of up to about 10minutes). In some embodiments a negligible etch rate is observed up toabout a 30 minute exposure or longer. It was found that the wet etchrate of these films in dilute hydrofluoric acid solution is less than0.3× that of thermal silicon oxide (TOX).

FIG. 4 shows fourier transform infrared spectroscopy (FTIR) analysis ofboron and carbon (B,C) films deposited according to the processdescribed with reference to FIG. 3 at a process temperature of about400° C. The FTIR analysis shows presence of C—H, B—H, B—C, B—B and C—Cbonds in the boron and carbon films. For example, the peak at about 2902cm⁻¹ can be attributed to C—H bonds, and the peak at about 2573 cm⁻¹ canbe attributed to B—H bonds in the film. The peaks at 1201 cm⁻¹ and 1051cm⁻¹ indicate presence of B—C, B—B and C—C bonds.

Boron and carbon (B,C) films were deposited on blanket wafers having adiameter of about 300 millimeters (mm) upon using the process asdescribed with reference to FIG. 3 at a process temperature of about400° C. The deposition was performed in a Pulsar® 3000 reactor chamberhaving a cross-flow configuration. A mean film thickness was measured atabout 35.58 nm after application of 1,000 cycles of the pulsed thermalCVD process of FIG. 3. The deposited boron and carbon film showedincreased thickness toward the center of the wafer, for example ascompared to the edge of the wafer, such as the leading edge of the wafer(e.g., a portion of the wafer edge further away from the wafer notch).Without being limited by any particular theory or mode of operation,such a thickness profile may indicate a surface reaction limited growthmechanism, and the thickness variations may be due to temperaturevariations of the susceptor on which the wafer was positioned. A surfacereaction limited growth can advantageously facilitate improved filmconformality performance for deposition of boron and carbon films upon3-D features.

Boron and carbon (B,C) films were deposited on blanket wafers in aPulsar® 3000 reactor chamber having a cross-flow configuration at aprocess temperature of about 450° C. The mean thickness of the depositedboron and carbon film was about 81.88 nm after application of 1,000cycles of the pulsed thermal CVD process of FIG. 3. As compared to theboron and carbon film deposited at about 400° C., the films deposited atabout 450° C. demonstrated an increased thickness. The deposited boronand carbon films had an increased thickness closer to the leading edgeof the blanket wafer, for example as compared to the boron and carbonfilms deposited at 400° C. Without being limited by any particulartheory or mode of operation, an increased thickness proximate to theleading edge may indicate a mass-transport limited film growthmechanism, versus a surface reaction limited growth mechanism.

FIGS. 5A-5D are scanning electron microscopy (SEM) images showingcross-section views of a boron and carbon (B,C) film deposited on a highaspect ratio trench structure 500 using the deposition process asdescribed with reference to FIG. 3. The boron and carbon film wasdeposited with a process temperature of about 400° C., in a Pulsar® 3000reactor chamber, and by applying 1,500 cycles of the reactant pulsefollowed by the purge step as described with reference to FIG. 3. FIG.5A shows, at 15 k× magnification, a SEM image of the high aspect ratiotrench structure 500. FIG. 5B shows, at 100 k× magnification, a SEMimage of an upper portion 502 of the high aspect ratio trench structure500. FIG. 5C shows, at 100 k× magnification, an SEM image of amid-section 504 of the high aspect ratio trench structure 500, and FIG.5D shows, at 100 k× magnification, a SEM image of a lower portion 506 ofthe high aspect ratio trench structure 500. A thickness of the depositedboron and carbon film in each of the upper, mid and lower portions ofthe high aspect ratio trench structure are shown in FIGS. 5B, 5C and 5D,respectively. As shown in FIG. 5, a relatively uniform film thicknesswas achieved on sides of the high aspect ratio trench structure at theupper, mid and lower portions of the trench structure, for exampledemonstrating the improved conformality of the deposited boron andcarbon film. For example, a film thickness of about 72 nm was measuredin the upper portion 502 of the high aspect ratio trench structure 500,a film thickness of about 69 nm was measured at a mid-section 504 of thetrench structure 500, and a film thickness of about 69 nm was measuredat a lower portion 506 of the trench structure 500, for exampledemonstrating that a conformality of greater than or equal to about 95%was achieved. Without being limited by any particular theory or mode ofoperation, deposition of the boron and carbon film at a processtemperature of about 400° C. or lower may facilitate deposition of thefilm in a surface reaction limited regime, facilitating improvedconformality of the deposited film.

Boron and Carbon Containing Silicon Nitride Films

As described herein, silicon nitride films can be deposited that includeboron and carbon components, and silicon nitride films comprising boronand carbon components can have a wide variety of applications, includingapplications in semiconductor device fabrication. Deposition of siliconnitride based films having desired characteristics using atomic layerdeposition (ALD) at reduced temperatures (e.g., at temperatures of lessthan about 500° C.), for example to provide processes with reducedthermal budgets, can be difficult. Silicon nitride based films depositedby conventional processes at lower process temperatures may providefilms having poor film quality, poor film conformality tothree-dimensional (3-D) structures upon which the silicon nitride basedfilm is deposited, undesirably high dry etch rates, and/or undesirablylow etch selectivity (e.g., etch selectivity to another material in asemiconductor device, including a thermal silicon oxide material, suchthat the silicon nitride film may withstand one or more subsequentthermal silicon oxide etch steps used in the device fabricationprocess).

The formula of a silicon nitride film is generally referred to herein asSiN for convenience and simplicity. However, the skilled artisan willunderstand that the actual formula of the silicon nitride can be SiNx,where x varies from about 0.5 to about 2.0, as long as some Si—N bondsare formed. In some cases, x preferably varies from about 0.9 to about1.7, more preferably from about 1.0 to about 1.5, and most preferablyfrom about 1.2 to about 1.4. Generally silicon nitride where Si has anoxidation state of +IV is formed and the amount of nitride in thematerial might vary.

The formula of a silicon nitride film comprising boron and carboncomponents is generally referred to herein as SiN(B,C) for convenienceand simplicity. However, the skilled artisan will understand that theactual formula of the SiN(B,C) can be SiN_(x)(B_(y),C_(z)). In someembodiments, for example, x can vary from about 0.5 to about 3.0, aslong as some Si—N bonds are formed. In some cases, x preferably variesfrom about 1.0 to about 2.0, and more preferably from about 1.3 to about1.8. In some embodiments, y can be between about 0.1 to about 5.0,including preferably from about 0.3 to about 3.0, and more preferablyfrom about 0.5 to about 1.5. For example, y can be about 1.5. In someembodiments, z can be from about 0.1 to about 5.0, including preferablyfrom about 0.2 to about 2.5, and more preferably from about 0.3 to about1.3. For example, z can be about 1.0.

One or more methods described herein can include an atomic layerdeposition (ALD) process and/or a chemical vapor deposition (CVD)process and can be used to form a silicon nitride based film, such as asilicon nitride film comprising boron and carbon components SiN(B,C). Insome embodiments, the silicon nitride films comprising boron and carboncomponents have one or more of improved conformal coverage ofthree-dimensional (3-D) features, a desirable dry etch rate, a desirablewet etch rate, and/or a desirable etch selectivity with respect toanother material (e.g., a thermal silicon oxide layer (TOX) in asemiconductor device). For example, a silicon nitride film includingboron and carbon components (e.g., for applications such as spacermaterial of gate features in semiconductor transistors, includingmulti-gate transistors such as FinFETs) deposited according to one ormore processes described herein can demonstrate improved step coverage,reduced etch rate in a wet etchant (e.g., resistance against wetetchant, such as a dilute hydrofluoric acid (HF or dHF) solution, suchas a 0.5 weight % HF solution), and/or a reduced wet etch ratio withrespect to a thermal silicon oxide material (e.g., a ratio of a wet etchrate of the silicon nitride based film to a wet etch rate of the thermalsilicon oxide material of less than about 1, including less than about0.5). In some embodiments, a silicon nitride film including boron andcarbon components can have a desirable dielectric constant (κ-value),for example a dielectric constant of less than about 7, including lessthan about 6, and less than about 5.5. For example, a silicon nitridefilm including boron and carbon components may have a dielectricconstant between about 4.8 and about 6, including between about 4.8 andabout 5.5.

In some embodiments, a silicon nitride ALD deposition process can beused to deposit a silicon nitride (SiN) film of a desired thickness andcomposition. ALD type processes are based on controlled, self-limitingsurface reactions. Gas phase reactions are avoided by contacting thesubstrate alternately and sequentially with reactants. Vapor phasereactants are separated from each other in the reaction chamber, forexample, by removing excess reactants and/or reactant byproducts fromthe reaction chamber between reactant pulses. For example, the ALDdeposition process can include contacting a substrate with a siliconreactant such that the silicon reactant adsorbs on the substratesurface, and subsequently contacting the substrate with a nitrogenreactant. A silicon reactant may comprise silicon-containing compoundswhich can contribute silicon to the growth of the silicon nitride film.A nitrogen reactant may comprise nitrogen-containing compounds which cancontribute nitrogen to the growth of the silicon nitride film. Exposureof the substrate to the silicon reactant and the nitrogen reactant canbe repeated as many times as required to achieve a film of a desiredthickness and composition. Excess reactants may be removed from thevicinity of the substrate, for example by purging from the reactionspace with an inert gas, after each contacting step. For example, thereactor chamber may be purged between reactant pulses. The flow rate andtime of each reactant, is tunable, as is the purge step, allowing forcontrol of the dopant concentration and depth profile in the film. Insome embodiments, the substrate can be moved to a space free orsubstantially free of reactants prior to purging the reactor chamber ofthe excess reactants and/or reaction byproducts.

In some embodiments, an ALD process for depositing the silicon nitride(SiN) film can include one or more cycles, each cycle comprising atleast two distinct processes or phases. The provision and removal of areactant from the reaction space may be considered a phase. In a firstprocess or phase, a first reactant comprising silicon is provided andforms no more than about one monolayer on the substrate surface. Thisreactant is also referred to herein as “the silicon precursor” or“silicon reactant.” In a second process or phase, a second reactantcomprising a nitrogen-containing compound is provided and reacts withthe adsorbed silicon precursor to form SiN. This second reactant mayalso be referred to as a “nitrogen precursor” or “nitrogen reactant.” Asdescribed herein, the second reactant may comprise ammonia (NH₃) and/oranother suitable nitrogen-containing compound. Additional processes orphases may be added and phases may be removed as desired to adjust thecomposition of the final film. In some embodiments for depositing asilicon nitride (SiN) film, one or more deposition cycles typicallybegins with provision of the silicon precursor followed by the nitrogenprecursor. In some embodiments, one or more deposition cycles beginswith provision of the nitrogen precursor followed by the siliconprecursor. One or more of the reactants may be provided with the aid ofa carrier gas, such as nitrogen (N₂), argon (Ar) and/or helium (He).

In some embodiments, a process for depositing a silicon nitride filmcomprising boron and carbon components (SiN(B,C)) having desirablecharacteristics can include a hybrid process comprising both an ALDprocess and a CVD process. For example the process for forming a siliconnitride film comprising boron and carbon components can comprise an ALDportion for depositing silicon nitride and a CVD portion forincorporating boron and carbon components into the growing film. Thesilicon nitride and boron and carbon components may in some embodimentsform a continuous film in which the silicon nitride and boron and carboncomponents do not form distinct layers or substantially do not formdistinct layers.

In some embodiments, no plasma is used in the deposition of the siliconnitride film comprising boron and carbon components. For example, aprocess for depositing the silicon nitride film comprising boron andcarbon components can include both a thermal ALD process and a thermalCVD process, including a pulsed thermal CVD process. In someembodiments, plasma of a nitrogen precursor is used in the ALD processfor depositing the silicon nitride. For example, a PEALD processcomprising plasma for a nitrogen precursor may be used for depositingsilicon nitride, and the PEALD process may be combined with a thermalCVD process for incorporating boron and carbon components into thesilicon nitride.

In some embodiments, the process for depositing a silicon nitride filmcomprising boron and carbon components (SiN(B,C)) can include an ALDprocess for depositing a silicon nitride (SiN) film (e.g., an ALDprocess comprising alternately and sequentially contacting the substratewith a silicon reactant, for example comprising octachlorotrisilane(Si₃Cl₈, OCTS), and a nitrogen reactant, for example comprising ammonia(NH₃)), and a decomposition process in which one or more boron reactantsdecomposes on the substrate surface for introducing the boron and carboncomponents into the silicon nitride film (e.g., a CVD process using oneor more boron reactants, for example comprising triethylboron (B(C₂H₅)₃,TEB, in which the TEB decomposes). In some embodiments, the ALD processfor depositing the SiN film can include contacting the substrate with asilicon reactant comprising hexachlorodisilane (Si₂Cl₆, HCDS). In someembodiments, the CVD process for introducing boron and carbon componentscan include contacting the substrate with a boron reactant comprisingtrialkylboron, such as trimethylboron (B(CH₃)₃, TMB or triethylboron(TEB)). In some embodiments, excess reactants and/or reaction byproducts can be removed by a purge step after each process (e.g., apurge step can be performed after a silicon reactant pulse, a nitrogenreactant pulse and/or a boron reactant pulse). For example, excesssilicon reactants and/or reaction byproducts can be removed from thereaction space prior to introducing the nitrogen reactants, such thatthe nitrogen reactant reacts with the adsorbed silicon reactant to forma monolayer of silicon nitride on the substrate. In some embodiments,the substrate can be moved to a space free or substantially free ofreactants prior to purging the reaction space.

In some embodiments a pulsed CVD process is used for the decompositionprocess. In some embodiments a pulsed CVD process is used in whichmultiple short pulses of the boron reactant are provided. In someembodiments a single, longer pulse of the boron reactant is provided. Insome embodiments the conditions are selected such that under the sameconditions the SiN is formed from surface reactions (ALD) while theboron reactant decomposes (CVD). In some embodiments, a pulsed CVDprocess for introducing boron and carbon components into the SiN filmfacilitates integration of the boron carbon process. In someembodiments, a pulsed CVD process for introducing boron and carboncomponents into the SiN film facilitates increased control in thequantity of boron and carbon components incorporated into the SiN film.In some embodiments, the boron reactant can also be provided under ALDconditions.

According to some embodiments of the present disclosure, the pressure ofthe reaction chamber during processing is maintained at about 0.01 Torrto about 50 Torr, preferably from about 0.1 Torr to about 10 Torr.

One or more parameters of the process for depositing the silicon nitridefilm and/or the process for introducing the boron and carbon componentscan be adjusted to provide a film having desired characteristics. Forexample, a flow rate of one or more boron reactants, and/or a processtemperature, of a CVD process for introducing the boron carbon andcomponents can be adjusted. For example, a duration of a reactant pulsefor providing one or more boron reactants in a pulsed CVD process can beadjusted. In some embodiments, one or more parameters of the ALD processfor depositing the SiN film can be adjusted, such as a processtemperature, a reactor chamber pressure, and/or a reactant exposureduration.

In some embodiments, the process for depositing a silicon nitride filmcomprising boron and carbon components can include one or more cycles ofthe process for providing the silicon nitride SiN film (e.g.,repetitions of the SiN process), and/or one or more cycles of theprocess for introducing the boron and carbon components (e.g.,repetitions of the boron carbon process). In some embodiments, thenumber of repetitions of the SiN process and the boron carbon processcan be tuned to provide a film of desirable characteristics. In someembodiments, the ratio of the number of repetitions of the SiN processto the number of repetitions of the boron carbon process is selected togive a desired film composition. In some embodiments, the SiN processcycle is repeated 2, 3, 4, 5, 6, 7, 8, 9, 10, or more times, for eachboron carbon process cycle. In some embodiments, a number of repetitionsof the SiN process cycle is followed by a number of repetitions of theboron carbon process cycle, where the number of repetitions of the SiNprocess cycle is different from the number of repetitions of the boroncarbon process cycle.

In some embodiments, a process for depositing a silicon nitride filmcomprising boron and carbon components can include a sequence comprisinga number of repetitions of an ALD process for deposition of the siliconnitride SiN film and/or a number of repetitions of a CVD process forintroducing the boron and carbon components, the number of repetitionsof each of the ALD process, the CVD process, and/or the total number ofrepetitions in the sequence of both the ALD process and CVD processbeing selected to provide a film having desired characteristics and/or adesired boron and carbon components composition. For example, a boronand carbon content may be adjusted to provide a film having a desiredetch performance (e.g., a wet etch rate and/or a dry etch rate), and/orconformality performance. In some embodiments, the number of repetitionsof the CVD process can be selected based on one or more parameters ofthe CVD process and/or the ALD process. In some embodiments, the numberof repetitions of the ALD process can be selected based on one or moreparameters of the ALD process and/or the CVD process. In someembodiments, the sequence including the number of repetitions of the ALDprocess cycle and the number of repetitions of the CVD process cycle canbe repeated to provide a film of a desired composition and/or thickness.

In some embodiments, the process for depositing a silicon nitride filmcomprising boron and carbon components does not include a plasmaenhanced process. That is, no plasma is used during the entire process.For example, the process can include both a thermal ALD process and apulsed thermal CVD process (e.g., thermal decomposition of one or moreboron reactants, such as decomposition of TEB).

FIG. 6 is a flow chart of an example of a process flow 600 for forming asilicon nitride film comprising boron and carbon components (e.g., aSiN(B,C) film). In block 602, a substrate can be exposed to one or morevapor phase silicon reactants (e.g., one or more silicon precursors). Alayer of silicon reactant is formed on the substrate surface. In someembodiments, the one or more vapor phase silicon reactants can adsorbonto a surface of the substrate. In some embodiments the one or moresilicon reactants at least partially decomposes at the substratesurface. In block 604, the substrate can be exposed to one or more vaporphase nitrogen reactants (e.g., a nitrogen precursor). For example, theone or more nitrogen reactants may interact with the one or more siliconreactants on the surface of the substrate (e.g., the one or morenitrogen reactants may react with the one or more silicon reactants onthe substrate surface to form silicon nitride (SiN)). In block 606, thesubstrate can be exposed to one or more vapor phase boron reactants(e.g., one or more boron and/or carbon precursors). The one or moreboron reactants may react with the silicon nitride on the substratesurface, thus introducing boron and carbon components into the film suchthat a silicon nitride film comprising boron and carbon components isformed. In some embodiments the one or more boron reactants decomposeson the substrate surface.

In some embodiments, one or more of the reactants may at least partiallydecompose on the substrate surface. For example, one or more of thesilicon, nitrogen or boron reactants is provided under chemical vapordeposition (CVD) conditions.

In some embodiments, a process for exposing a substrate to a siliconreactant, a nitrogen reactant, and/or a boron reactant can include achemical vapor deposition (CVD) process. In some embodiments, each ofexposing a substrate to a silicon reactant, a nitrogen reactant, and aboron reactant can include a CVD process, including for example a pulsedCVD process.

In some embodiments, exposing a substrate to a silicon reactant, anitrogen reactant, and/or a boron reactant can include a vapor phasedeposition process in which one or more reactants decompose tofacilitate formation of the SiN(B,C) film.

In some embodiments, the ALD and/or the CVD processes can be a plasmaenhanced process (e.g., a direct plasma process and/or a remote plasmaprocess). In some embodiments, the ALD and/or the CVD processes do notinclude a plasma enhanced process. For example, the ALD process can be athermal ALD process.

In some embodiments, a process for exposing a substrate to a siliconreactant, a nitrogen reactant, and/or a boron reactant may overlap, orbe combined. For example, one or more of the silicon reactant, nitrogenreactant, and/or boron reactant may be provided in pulses that partiallyor completely overlap.

In some embodiments, a nitrogen-containing gas (e.g., nitrogen gas (N₂)and/or ammonia (NH₃)) can be fed continuously throughout a process fordepositing a SiN(B,C) film (e.g., the nitrogen-containing gas can serveas a carrier gas and/or as a reactant). For example, thenitrogen-containing gas can serve as a carrier gas for reactants in aplasma process (e.g., used for generating a nitrogen-containing plasma).In some embodiments, the nitrogen-containing gas is fed continuously orsubstantially continuously into the reaction chamber throughout adeposition process, for example including while reactant pulses of asilicon reactant and/or a boron reactant are introduced into the reactorchamber. Nitrogen-containing gas flow rate and/or a concentration of thenitrogen flow can be adjusted during the deposition process, forexample, during pulsing of the silicon reactant and/or boron and/orcarbon reactant.

A variety of silicon reactants may be suitable. In some embodiments, asuitable silicon reactant in a process for depositing a silicon nitridefilm can include at least one of silicon halides, silicon alkylamines,silicon amines and/or silanes (e.g., including silanes comprising one ormore alkyl groups). For example, a suitable silicon reactant can includea silicon chloride. In some embodiments, a silicon reactant can includea halosilane. In some embodiments, a silicon reactant can include analkyl silicon compound comprising a halide. In some embodiments, asilicon reactant can be alkyl silane. In some embodiments, a siliconreactant can include octachlorotrisilane (Si₃Cl₈, OCTS). In someembodiments, a silicon reactant can include hexachlorodisilane (Si₂Cl₆,HCDS).

Suitable nitrogen reactants can include a variety of nitrogen-containingreactants. In some embodiments, a nitrogen reactant can include ahydrogen bonded to a nitrogen (N—H). In some embodiments, a suitablenitrogen reactant can be ammonia (NH₃). In some embodiments, a suitablenitrogen reactant can be hydrazine (N₂H₄). In some embodiments, asuitable nitrogen reactant can comprise one or more reactive speciesgenerated by a nitrogen-containing plasma, including for examplenitrogen-containing radicals. In some embodiments, a suitable nitrogenreactant can include nitrogen atoms.

In some embodiments, a suitable boron reactant can include a boroncompound having at least one organic ligand. In some embodiments, theorganic ligand can have double and/or triple bonds. In some embodiments,the organic ligand can be a cyclic ligand. In some embodiments, theorganic ligand can comprise delocalized electrons. In some embodiments,a suitable boron reactant can include trialkylboron compounds. In someembodiments, a suitable boron reactant can include triethylboron(B(C₂H₅)₃, TEB). In some embodiments, a suitable boron reactant caninclude trimethylboron (B(CH₃)₃, TMB). In some embodiments, a suitableboron reactant can include trialkylboron compounds having linear orbranched alkyl groups, including for example linear or branched C₃-C₈,and more preferably including linear or branched C₃-C₅. Suitable boronreactants can include a variety of other boron-containing reactants. Insome embodiments, a boron reactant can include a boron halide, analkylboron, and/or a borane. In some embodiments, a boron reactant caninclude boron halides, borane halides and complexes thereof. Forexample, a suitable boron halide can have a boron to halide ratio ofabout 0.5 to about 1.

Suitable boranes can include compounds according to formula I or formulaII.B_(n)H_(n+x)  (formula I)

Wherein n is an integer from 1 to 10, preferably from 2 to 6, and x isan even integer, preferably 4, 6 or 8.B_(n)H_(m)  (formula II)

Wherein n is an integer from 1 to 10, preferably form 2 to 6, and m isan integer different than n, from 1 to 10, preferably from 2 to 6.

Of the above boranes according to formula I, examples includenido-boranes (B_(n)H_(n+4)), arachno-boranes (B_(n)H_(n+6)) andhyph-boranes (B_(n)H_(n+8)). Of the boranes according to formula II,examples include conjuncto-boranes (B_(n)H_(m)). Also, borane complexessuch as (CH₃CH₂)₃N—BH₃ can be used.

In some embodiments, suitable boron reactants can include boranehalides, particularly fluorides, bromides and chlorides. An example of asuitable compound is B₂H₅Br. Further examples comprise boron halideswith a high boron/halide ratio, such as B₂F₄, B₂Cl₄ and B₂Br₄. It isalso possible to use borane halide complexes.

In some embodiments, halogenoboranes according to formula III can besuitable boron reactants.B_(n)X_(n)  (formula III)

Wherein X is Cl or Br and n is 4 or an integer from 8 to 12 when X isCl, or n is an integer from 7 to 10 when X is Br.

In some embodiments, carboranes according to formula IV can be suitableboron reactants.C₂B_(n)H_(n+x)  (formula IV)

Examples of carboranes according to formula IV include closo-carboranes(C2B_(n)H_(n+2)), nido-carboranes (C₂B_(n)H_(n+4)) andarachno-carboranes (C₂B_(n)H_(n+6)).

In some embodiments, amine-borane adducts according to formula V can besuitable boron reactants.R₃NBX₃  (formula V)

Wherein R is linear or branched C1 to C10, preferably C1 to C4 alkyl orH, and X is linear or branched C1 to C10, preferably C1 to C4 alkyl, Hor halogen.

In some embodiments, aminoboranes where one or more of the substituentson B is an amino group according to formula VI can be suitable boronreactants.R₂N  (formula VI)

Wherein R is linear or branched C1 to C10, preferably C1 to C4 alkyl orsubstituted or unsubstituted aryl group.

An example of a suitable aminoborane is (CH₃)₂NB(CH₃)₂.

In some embodiments, a suitable boron reactant can include a cyclicborazine (—BH—NH—)₃ and/or its volatile derivatives.

In some embodiments, alkyl borons or alkyl boranes can be suitable boronreactants, wherein the alkyl is typically linear or branched C1 to C10alkyl, preferably C2 to C4 alkyl.

In some embodiments, the substrate on which deposition of a siliconnitride film comprising boron and carbon is desired, such as asemiconductor workpiece, is loaded into a reactor chamber. The reactorchamber may be part of a cluster tool in which a variety of differentprocesses in the formation of an integrated circuit are carried out. Insome embodiments, one or more deposition processes described herein canbe performed in a batch reactor, including for example in a mini-batchreactor (e.g., a reactor having a capacity of eight substrates or less)and/or a furnace batch reactor (e.g., a reactor having a capacitor offifty or more substrates). In some embodiments, one or more depositionprocesses described herein can be performed in a single wafer reactor.In some embodiments, a spatial reactor chamber may be suitable (e.g., aspatial ALD reactor chamber). In some embodiments, a reactor chamberhaving a cross-flow configuration can be suitable. In some embodiments,a reactor chamber having a showerhead configuration can be suitable.

Exemplary single wafer reactors are commercially available from ASMAmerica, Inc. (Phoenix, Ariz.) under the tradenames Pulsar® 2000 andPulsar® 3000 and ASM Japan K.K (Tokyo, Japan) under the tradename Eagle®XP and XP8. Exemplary batch ALD reactors are commercially available fromand ASM Europe B.V (Almere, Netherlands) under the tradenames A400™ andA412™.

FIG. 7 is a flow chart showing another example of a process 700 forforming a silicon nitride film comprising boron and carbon components(e.g., a SiN(B,C) film). The process 700 can include a sequence 702having a process 704 for forming silicon nitride on a substrate surfaceand a process 712 for introducing boron and carbon components into thesilicon nitride. In some embodiments, the sequence 702 can be repeated anumber of times to form a SiN(B,C) film having a desired compositionand/or thickness. The ratio of the number of times process 704 isperformed to the number of times the process 712 is performed can bevaried to tune the concentration of boron and carbon components in thefilm and thus to achieve a film with desired characteristics. Forexample, the number of times process 704 is repeated relative to thenumber of times the process 712 is repeated can be selected to provide afilm with desired boron and carbon components content.

The process 704 for forming silicon nitride on a substrate surface caninclude blocks 706, 708 and 710. In block 706, the substrate can beexposed to one or more silicon reactants. In block 708, the substratecan be exposed to one or more nitrogen reactants. In block 710, blocks706 and 708 can be repeated a number of times (e.g., a number of cyclesof the process 704). In some embodiments, exposing the substrate to theone or more silicon reactants in block 706 can comprise exposing thesubstrate to a silicon reactant pulse, and exposing the substrate to theone or more nitrogen reactants in block 708 can comprise exposing thesubstrate to a nitrogen reactant pulse. In some embodiments, a siliconreactant pulse of block 706 and a nitrogen reactant pulse of block 708are separated by a purge step (not shown) configured for removing excesssilicon reactant and/or reaction byproduct from the reactor chamber. Apurge step may comprise flowing of purge gas, and/or evacuating thereactor chamber (e.g., by drawing a vacuum upon the reactor chamber) soas to remove or substantially remove excess reactants and/or reactionbyproducts. In some embodiments, excess nitrogen reactant and/orreaction byproducts are removed prior to performing the repetitionprocess in block 710, for example by performing a purge step (not shown)after exposing the substrate to the one or more nitrogen reactants inblock 708. In some embodiments, process 704 is an ALD process. In someembodiments, process 704 is a CVD process, where at least one of thereactants at least partially decomposes on the substrate surface. Insome embodiments, the pulses of the silicon and nitrogen reactants mayat least partially overlap.

The process 712 for introducing boron and carbon components into thesilicon nitride can include blocks 714 and 716. In block 714, thesubstrate can be exposed to one or more boron reactants. In block 716,block 714 can be repeated a number of times (e.g., a number of cycles ofthe process 712). In some embodiments, exposing the substrate to the oneor more boron reactants comprises exposing the substrate to a boronreactant pulse. For example, in block 716, the boron reactant pulse ofblock 714 can be repeated a number of times. In some embodiments, eachboron reactant pulse can be separated by a purge step (not shown)configured to remove excess boron reactants and/or reaction byproducts.In some embodiments, a single boron reactant pulse is provided (e.g., arepetition of process 714 is not performed). The one or more boronreactants are provided under CVD conditions in some embodiments, suchthat the one or more boron reactants decompose on the substrate surface.

In some embodiments, a process for forming a SiN(B,C) film (e.g.,process 700 of FIG. 7) can be a hybrid process including both ALD andCVD processes. For example, a process for forming the silicon nitride(SiN) film (e.g., process 704 of FIG. 7) can include an ALD process, anda process for introducing boron and carbon components into the siliconnitride (SiN) film (e.g., process 712 of FIG. 7, so as to form aSiN(B,C) film) can include a CVD process.

In some embodiments plasma is not used in either of 704 or 712. Forexample, process 704 and/or 712 can include a thermal process, such as athermal ALD process and/or a thermal CVD process.

A silicon reactant of an ALD process for providing a silicon nitridefilm (SiN) may comprise octachlorotrisilane (Si₃Cl₈, OCTS) and/orhexachlorodisilane (Si₂Cl₆, HCDS), and a nitrogen reactant of the ALDprocess may comprise ammonia (NH₃). Exposing a substrate to the siliconreactant (e.g., block 706 of FIG. 7) can include exposing the substrateto Si₃Cl₈ and/or Si₂Cl₆. For example, Si₃Cl₈ and/or Si₂Cl₆ can be fedinto a reactor chamber (e.g., a silicon reactant pulse) for a durationof time, including for example with the aid of a nitrogen carrier gas.Exposing the substrate to the nitrogen reactant (e.g., block 708 of FIG.7) can include exposing the substrate to NH₃. For example, NH₃ can befed into a reactor chamber (e.g., a nitrogen reactant pulse) for aduration of time, including for example with the aid of a nitrogencarrier gas. The pulse length for a silicon reactant pulse and/or anitrogen reactant pulse can be from about 0.05 seconds to about 5.0seconds, about 0.1 seconds to about 3 seconds or about 0.2 seconds toabout 1.0 second. For example, a nitrogen reactant pulse and/or asilicon reactant pulse can be about 1 second.

As described herein, a reactant pulse for delivering one or morereactants into a reactor chamber in an ALD process can be followed by apurge step, such as for removal of an excess reactant and/or a reactionbyproduct from the vicinity of the substrate surface. A gas such asnitrogen (N₂), argon (Ar) and/or helium (He) can be used as a purge gasto aid in the removal of the excess reactant and/or reaction byproduct.In some embodiments, a purge step of an ALD process can be about 1second to about 20 seconds, about 1 second to about 15 seconds or about1 second to about 10 seconds, including about 5 seconds. For example,one cycle of an ALD process for exposing a substrate to a siliconreactant and/or a nitrogen reactant can include a reactant pulse ofabout 0.5 seconds, followed by a purge step of about 5 seconds. In someembodiments, one cycle of an ALD process can include a silicon reactantpulse of about 0.5 seconds, followed by a purge step of about 5 seconds,followed by a nitrogen reactant pulse of about 0.5 seconds, and thenfollowed by a purge step of about 5 seconds.

A cycle of the ALD process may be repeated a number of times until afilm of the desired thickness and/or composition is obtained. In someembodiments the deposition parameters, such as the reactant flow rate,reactant flow duration, purge step duration, and/or reactantsthemselves, may be varied in one or more deposition cycles during theALD process in order to obtain a film with the desired characteristics.For example, one or more deposition parameters of an ALD process cyclemay be different from that of another ALD process cycle.

As described herein, in some embodiments, a process for depositing asilicon nitride film comprising boron and carbon components (e.g., aSiN(B,C) film) can include a chemical vapor deposition (CVD) process. ACVD process for introducing boron and carbon components into a siliconnitride film can include decomposition of one or more reactants and/orchemical interaction between multiple reactants on the silicon nitridefilm. For example, a reactant can be fed into a reactor chamber, thedecomposition of which facilitates formation of the desired film. Insome embodiments, a suitable boron reactant can include triethylboron(B(C₂H₅)₃, TEB) and/or trimethylboron (B(CH₃)₃, TMB). For example, TEBfed into the reactor chamber may decompose on the silicon nitride filmto facilitate introduction of boron and carbon components into thesilicon nitride film.

In some embodiments, a pulsed CVD process can be used. In someembodiments, the process for depositing the SiN(B,C) film includes anALD process configured to provide a silicon nitride SiN film on asubstrate surface, and a CVD process performed subsequent to at leastone cycle of the ALD process, the CVD process being configured forintroducing boron and carbon components into the silicon nitride film soas to form the SiN(B,C) film (e.g., a pulsed CVD process for deliveringpulses of one or more boron reactants into the reactor chamber). In someembodiments, the CVD process can be repeated a number of times toprovide a SiN(B,C) film having a desired composition (e.g., repeatingfor a number of times a cycle of a CVD process including a reactantpulse followed by a purge process). In some embodiments, the CVD processfor introducing boron and carbon components is not a pulsed CVD process,such that a boron reactant is fed in a continuous or substantiallycontinuous stream into the reactor chamber to achieve a SiN(B,C) filmhaving a desired boron and carbon components content.

A pulsed CVD process can include feeding a reactant gas (e.g., areactant pulse) into a reactor chamber for a duration of time. In someembodiments, the reactant pulse of a CVD process can have a durationfrom about 0.05 seconds to about 5.0 seconds, about 0.1 seconds to about3 seconds or about 0.2 seconds to about 1.0 second. For example, areactant pulse can be about 0.5 seconds.

In some embodiments, an interval between two reactant pulses cancomprise discontinuing flow of the one or more reactants of the reactantpulse. An interval between reactant pulses may have a duration of about1 second to about 20 seconds, including about 1 second to about 15seconds, or about 1 second to about 10 seconds. For example, theinterval can be about 5 seconds. In some embodiments, the intervalcomprises transport of the substrate to a space free or substantiallyfree of reactants. In some embodiments, the interval comprises a purgestep. For example, the interval may comprise transport of the substrateto a space free or substantially free of reactants, and a purge step.For example, a pulse for delivering one or more reactants into a reactorchamber for a pulsed CVD process can be followed by a purge step, suchas for removal of an excess reactant and/or a reaction byproduct fromthe vicinity of the substrate surface. A purge step can include flow ofone or more inert gases through the reactor chamber (e.g., argon (Ar),helium (He), and/or nitrogen (N₂)). In some embodiments, each reactantpulse can be followed by a purge step. A purge step can include removalof an excess reactant and/or byproducts from the vicinity of thesubstrate. In some embodiments, a purge step of a CVD process can have aduration of about 1 second to about 20 seconds, about 1 second to about15 seconds or about 1 second to about 10 seconds. For example, a purgeprocess can be about 5 seconds. Other durations for the reactant pulseand/or the purge process may also be suitable, as can be determined bythe skilled artisan given the particular circumstances.

A suitable duration of time in which a reactant gas is provided into areactor chamber and/or a duration of a purge step, a gas flow rate inthe reactant pulse and/or the purge step, can depend on one or moreparameters of the reaction process, for example, adjusting a reactantpulse duration and/or reactant pulse gas flow rate, and/or a purge stepduration and/or purge step gas flow rate, such that desired reactantsare provided to and/or removed from the vicinity of the substratesurface.

As described herein, a process for depositing a SiN(B,C) film caninclude a sequence (e.g., sequence 702 of FIG. 7) having a number ofrepetitions of a process for providing a silicon nitride film, followedby a number of repetitions of a process for introducing boron and carboncomponents into the silicon nitride film. In some embodiments, thesequence can be repeated for a number of times (e.g., the sequence beingrepeated Z number of times) to provide a SiN(B,C) film having a desiredcomposition and/or thickness. For example, a process for forming aSiN(B,C) film can include a sequence having a number cycles of an ALDprocesses for depositing a silicon nitride SiN film followed by a numberof cycles of an CVD process for introducing boron and carbon componentsinto the silicon nitride SiN film, the sequence being repeated for anumber of times to provide a SiN(B,C) film of a desired compositionand/or thickness.

In some embodiments, a sequence, including a number of cycles of an ALDprocess for depositing a silicon nitride film followed by a number ofcycles of a CVD process for introducing boron and carbon components intothe silicon nitride film, can be repeated about 1 time to about 150times, including about 25 times to about 75 times. For example, thesequence can be repeated about 75 times. For example, the sequence canbe repeated 100 times.

A number of cycles of a process for providing a silicon nitride (SiN)film (e.g., X cycles of an ALD process, such as repeating a number oftimes or performing a number of cycles of process 704 of FIG. 7) and/ora number of cycles of a process for introducing boron and carboncomponents into the silicon nitride (e.g., Y cycles of a CVD process,such as repeating a number of times or performing a number of cycles ofprocess 712 of FIG. 7) in a sequence may be selected to achieve desiredfilm characteristics. For example, a sequence can include a number ofcycles of an ALD process followed by a number of cycles of a CVDprocess. The number of ALD cycles and/or the number of CVD cycles may bevaried to provide a SiN(B,C) film comprising a desired compositionand/or thickness. For example, the number of cycles of the process forintroducing boron and carbon components can be selected to provide aSiN(B,C) film having a desired boron and carbon components content(e.g., for demonstrating a desired etch rate, conformality performance,and/or other film characteristic).

In some embodiments, the number of cycles of a process for providingboron and carbon components of the silicon nitride film within asequence can be from about one cycle to about twenty cycles, includingfrom about one cycle to about ten cycles. In some embodiments, theprocess for providing the boron and carbon components can be repeatedfive times. For example, a pulsed CVD process for introducing boron andcarbon components into a silicon nitride film can be repeated threetimes within a sequence. The cycling of the process for providing theboron and carbon components can be performed prior to additional cyclingof a process for depositing a silicon nitride SiN film. For example, asequence of a SiN(B,C) film deposition process can include first cyclinga number of times a process for depositing a silicon nitride SiN film,and second followed by cycling for a number of times a process foradding the boron and carbon components to the SiN film.

In some embodiments, a ratio of a number of cycles of a process fordepositing a silicon nitride film to a number of cycles of a process forintroducing a boron and carbon components (e.g., a ratio of Y:X) withina sequence can be about 1:1 to about 100:1, including about 3:1 to about50:1. In some embodiments, the ratio of the number of cycles for theprocess of depositing a silicon nitride film to the number of cycles ofthe process for introducing boron and carbon components within asequence can be about 5:1 to about 20:1. The ratio can be expressed as apercentage or a boron carbon process fraction, such as a percentage ofthe total number of cycles in a sequence which is a process forintroducing the boron and carbon components. For example, a boron carbonprocess fraction or a percentage of the total number of cycles in asequence which is a process for introducing the boron and carboncomponents can be adjusted to provide a SiN(B,C) film having desiredcomposition. The percentage or boron carbon process fraction may becalculated by the following formula: X/(X+Y)*100%. In some embodiments,the boron carbon process fraction or the percentage of the total numberof cycles in a sequence which is a process for introducing the boron andcarbon components can be about 0.01% to about 50%, including about 5% toabout 20%. For example, the boron carbon process fraction can be about10%. For example, a process having a boron carbon process fraction ofabout 5.0% to about 10% can form a SiN_(x)(B_(y),C_(z)) film where x canbe about 1.3 to about 1.8, y can be about 0.5 to about 1.5, and z can beabout 0.3 to about 1.3.

A first phase and/or a second phase of an ALD process, and/or a CVDprocess can be performed at a process temperature of about 25° C. toabout 800° C., including about 100° C. to about 600° C. The processtemperature as referred to herein can comprise a temperature of areactor chamber susceptor, a reactor chamber wall, and/or a temperatureof the substrate itself. In some embodiments, a first phase and/or asecond phase of an ALD process and/or a CVD process can be performed ata process temperature of about 150° C. to about 500° C. For example, oneor both of the first phase and the second phase of the ALD process,and/or the CVD process can be performed at a process temperature ofabout 200° C. to about 400° C. For example, a first phase and/or asecond phase of one or more cycles of an ALD process described hereinmay be performed in a reactor chamber having a susceptor, a substrateand/or a reactor chamber wall heated to a temperature of about 200° C.to about 400° C., such as a temperature of about 400° C. For example,the CVD process can be performed in a reactor chamber having asusceptor, a substrate and/or a reactor chamber wall heated to atemperature of about 400° C. In some embodiments, the CVD process forintroducing boron and carbon components into the silicon nitride can beperformed at a process temperature of less than 400° C., including forexample from about 325° C. to about 400° C., and about 350° C. to about400° C.

In some embodiments, a temperature of a process for depositing a siliconnitride SiN film and/or a process for introducing a boron and carboncomponents can be sufficiently high to facilitate a decomposition of oneor more reactants (e.g., a silicon reactant and/or a nitrogen reactantof an ALD process, and/or a boron reactant of a CVD process), and/orreaction between reactants and/or between reactants and the substratesurface, while providing a process with a reduced thermal budget. Insome embodiments, a process temperature for depositing the siliconnitride SiN film and/or introducing boron and carbon components can beabout 325° C. to about 800° C., including about 350° C. to about 600°C., about 400° C. to about 600° C., or about 375° C. to about 450° C.For example, a CVD process for introducing boron and carbon componentsinto a silicon nitride can be performed at a process temperature ofabout 400° C. (e.g., a CVD process including decomposing the boronreactant TEB for introducing the boron and carbon components to thesilicon nitride film). In some embodiments, an ALD process fordepositing the silicon nitride SiN film can be performed at a processtemperature of about 400° C. (e.g., an ALD process in which one or morereactants may decompose in forming the SiN film). In some embodiments, atemperature of the ALD process can be different from a temperature ofthe CVD process. In some embodiments, the same temperature is used forthe ALD process for forming the silicon nitride SiN film and the CVDprocess for adding boron and carbon components to the SiN film.

An example of a deposition process for forming a SiN(B,C) film can beperformed (e.g., in a Pulsar®3000 chamber, commercially available fromASM America, Inc. of Phoenix, Ariz.) using a thermal ALD process forforming a silicon nitride SiN film. The thermal ALD process can beperformed at a process temperature of about 400° C. on a 300 millimeter(mm) wafer, including a silicon reactant comprising octachlorotrisilane(Si₃Cl₈, OCTS) fed into the reactor chamber with a carrier gas (e.g.,nitrogen) such that a silicon reactant pulse has a duration of about 1second and is followed by a purge process (e.g., using purge gascomprising nitrogen) having a duration of about 5 seconds. The OCTS maybe stored in a bubbler at a temperature of about 40° C. and providedinto the reactor chamber from the bubbler (e.g., a mass flow rate of theOCTS may be controlled by controlling the extent to which a valve fordelivering the OCTS into the reactor chamber is kept open). The thermalALD process can include a nitrogen reactant comprising ammonia (NH₃) fedinto the reactor chamber such that the nitrogen reactant pulse hasduration of about 1 second and which is followed by a purge process(e.g., using purge gas comprising nitrogen) having a duration of about 5seconds. The NH₃ may be provided into the reactor chamber from a gassource maintained at a pressure of about 1.5 Bar (e.g., a mass flow rateof the NH₃ may be controlled by controlling the extent to which a valvefor delivering the NH₃ into the reactor chamber is kept open). The ALDprocess can be cycled a number of times. A number of cycles of the ALDprocess can be followed by a number of cycles of a thermal CVD processfor introducing boron and carbon components into the SiN film. Thethermal CVD process can be performed at a temperature of about 400° C.and can include a boron reactant pulse for providing a boron reactantcomprising triethylboron (B(C₂H₅)₃, TEB) into the reactor chamber, wherethe boron reactant pulse can have a duration of about 0.5 seconds. Theboron reactant pulse may be followed by a purge step (e.g., using purgegas comprising nitrogen) having a duration of about 5 seconds. Forexample, the SiN(B,C) deposition process can include a sequencecomprising 19 cycles of the ALD process followed by 2 cycles of the CVDprocess (e.g., providing a boron carbon process fraction of about 10%),where the sequence is repeated 75 times.

A composition of a silicon nitride film comprising boron and carboncomponents may be adjusted, for example, by increasing or decreasing aboron carbon process fraction of the process for depositing the film.For example, a boron and carbon content of the film may be adjusted byadjusting a boron carbon process fraction of the film fabricationprocess. In some embodiments, the silicon nitride film comprising boronand carbon components can have about 0.1 atomic % to about 50 atomic %of boron, including about 1 atomic % to about 35 atomic % of boron. Forexample, the silicon nitride film comprising boron and carbon componentscan have about 5 atomic % to about 30 atomic % boron. In someembodiments, the silicon nitride film comprising boron and carboncomponents can have about 0.1 atomic % to about 50 atomic % of carbon,including about 1 atomic % to about 35 atomic % of carbon. For example,the silicon nitride film comprising boron and carbon components can haveabout 5 atomic % to about 30 atomic % carbon. In some embodiments, asilicon and/or a nitrogen content can be adjusted by adjusting a boroncarbon process fraction of the film fabrication process.

In some embodiments, a SiN(B,C) film formed according to one or moreprocesses described herein can have a desirable dielectric constant(κ-value). A dielectric constant of a SiN(B,C) film may be lower thanthat of conventional silicon nitride films. In some embodiments aSiN(B,C) film can have a dielectric constant less than about 7,including less than about 6. For example, a SiN(B,C) film may have adielectric constant between about 4.8 and about 7, including betweenabout 4.8 and 6, and between about 4.8 and about 5.5. In someembodiments, a dielectric constant of a SiN(B,C) film can be adjusted byadjusting a boron carbon process of the film fabrication process. Insome embodiments, a SiN(B,C) film having a dielectric constant of about5.5 can be formed using a deposition process having a boron carbonprocess fraction of about 10% or higher. SiN(B,C) films with reduceddielectric constants, for example dielectric constants less than that ofconventional silicon nitride films, used for certain applications of asemiconductor device (e.g., as a spacer material for a transistor gatefeature) may facilitate improvements in one or more device electricalparameters, including a reduction in device parasitic capacitances.

As described herein, a SiN(B,C) film can be a sacrificial film in asemiconductor device fabrication process. For example, the SiN(B,C) filmmay be selectively removed in an etch process. In some embodiments, asacrificial SiN(B,C) film can be selectively removed during fabricationof a semiconductor device using an etch process comprising chlorine (Cl)and/or fluorine (F), such as chlorine and/or fluorine containing plasmaprocesses. In some embodiments, a SiN(B,C) film may form a part of afinished semiconductor device. For example, the SiN(B,C) film may bemore resistant to etch than one or more other materials used in thefabrication of the semiconductor device.

The SiN(B,C) film may have a desired etch selectivity with respect toanother material in the device. For example, an etch selectivity of theSiN(B,C) film may be tuned by adjusting a boron and carbon componentscontent of the film (e.g., by adjusting a boron carbon process fractionof the film fabrication process). In some embodiments, the SiN(B,C) filmmay be etched by a dry etch process and/or a wet etch process. Forexample, the SiN(B,C) film may be etched by a plasma etch process,including a fluorine-containing plasma. In some embodiments, theSiN(B,C) film can have a etch selectivity (e.g., a dry etch and/or a wetetch selectivity) of about 5 or greater with respect to another materialof the device, including a selectivity of about 10 or greater, about 20or greater, or about 50 or greater.

In some embodiments, the SiN(B,C) film can demonstrate a desired wetetch selectivity, such as a wet etch selectivity with respect to athermal silicon oxide (TOX) layer. For example, the SiN(B,C) film may bemore resistant to wet etch than the thermal silicon oxide layer, havinga ratio of a wet etch rate of the SiN(B,C) film to a wet etch rate of athermal silicon oxide layer less than about 1, less than about 0.5, orless than about 0.3. In some embodiments, the ratio of a wet etch rateof the SiN(B,C) film to a wet etch rate of the thermal silicon oxidelayer can be less than about 0.1.

In some embodiments, one or more silicon nitride films comprising boronand carbon components (SiN(B,C)) formed according to one or moreprocesses described herein can have a desired etch rate in a number ofetchant solutions. In some embodiments, a silicon nitride filmcomprising boron and carbon components (e.g., a SiN(B,C) film) may beresistant or substantially resistant to one or more wet etchants. Forexample, a SiN(B,C)) film can have an etch rate of less than about 1nanometers per minute (nm/min), including less than about 0.5 nm/min,including less than about 0.2 nm/min and including less than about 0.1nm/min, in one or more of the following etchant solutions at theprovided temperatures: a concentrated nitric acid HNO₃ solution (e.g., asolution having a HNO₃ concentration of about 65 to about 75 weight %)at about 80° C., a 5.5 weight % hydrofluoric acid (HF) at roomtemperature (e.g. a temperature of about 25° C.), a solution having aratio of nitric acid:hydrofluoric acid:water (HNO₃:HF:H₂O) at about1:1:5 at about room temperature (e.g., a temperature of about 25° C.),an aqueous solution of sodium hydroxide (NaOH) having a concentration ofNaOH of about 10 weight % at about room temperature (e.g., a temperatureof about 25° C.), a concentrated hydrochloric acid (HCl) solution (e.g.,a solution having an HCl concentration of about 35 to about 40 weight %)at about room temperature (e.g., a temperature of about 25° C.), and aconcentrated sulfuric acid solution (H₂SO₄) (e.g., a solution having aH₂SO₄ concentration of greater than about 90 weight %) at about roomtemperature (e.g., a temperature of about 25° C.).

In some embodiments, a silicon nitride film comprising boron and carboncomponents (e.g., a SiN(B,C) film) may be resistant or substantiallyresistant to a wet etchant comprising phosphoric acid (H₃PO₄) at aconcentration of about 85 weight % at about room temperature (e.g., atemperature of about 25° C.). In some embodiments, a silicon nitridefilm comprising boron and carbon components (e.g., a SiN(B,C) film) maybe resistant or substantially resistant to one or more of the followingwet etchants (e.g., an etch rate of less than about 3 nanometers/min(nm/min)), and after a dip in a 1 weight % hydrofluoric acid (HF) forabout 2 minutes): phosphoric acid (H₃PO₄) at a concentration of about 85weight % at about room temperature (e.g., a temperature of about 25°C.), aqueous sodium hydroxide (NaOH) having a concentration of about 10weight % solution at about room temperature (e.g., a temperature ofabout 25° C.), a hydrochloric acid (HCl) solution having a concentrationof about 35 to about 40 weight % (e.g., about 37 weight %) at about roomtemperature (e.g., a temperature of about 25° C.), and a sulfuric acidsolution (H₂SO₄) having a concentration of greater than about 90 weight% (e.g., 98 weight %) at about room temperature (e.g., a temperature ofabout 25° C.).

In some embodiments, a SiN(B,C) film can have an etch rate of more thanabout 1.0 nanometers per minute (nm/min) in a solution having a ratio ofhydrogen peroxide:hydrofluoric acid:water (H₂O₂:HF:H₂O) of about 5:5:90,by volume, at about room temperature (e.g., at a temperature of about25° C.). In some embodiments, a SiN(B,C)) film can be etched subsequentto being exposed to a treatment in oxygen-containing atmosphere,including for example ozone and/or an oxygen-containing plasma (e.g., aplasma comprising oxygen atoms and/or other oxygen-containing radicals).

As described herein, a SiN(B,C) film may be deposited on and/or over athree-dimensional (3-D) structure while demonstrating desiredconformality or step coverage. In some embodiments, a SiN(B,C) film candemonstrate desired conformality or step coverage over athree-dimensional structure having an aspect ratio of about 2:1 orhigher, including about 3:1 or higher, about 5:1 or higher, or about 8:1or higher. In some embodiments, a SiN(B,C) film can demonstrate desiredconformality or step coverage over a three-dimensional structure havingan aspect ratio of about 10:1 or higher, about 25:1 or higher, or about50:1 or higher. In some embodiments, a SiN(B,C) film can demonstrate adesired step coverage over one or more features as described herein,including a step coverage of about 80% or higher, including about 90% orhigher, about 95% or higher, or about 100%. In some embodiments, aSiN(B,C) film can demonstrate a step coverage of about 80% or higher,including about 90% or higher, about 95% or higher, or about 100%, whenformed on three-dimensional structures having an aspect ratio of up toabout 250:1, including up to about 150:1 and up to about 100:1.

In some embodiments, a portion of a SiN(B,C) film deposited on asidewall of a three-dimensional structure can demonstrate a desired etchrate, for example, as compared to an etch rate of a portion of the filmdeposited on a top surface of the three-dimensional feature. In someembodiments, a portion of a SiN(B,C) film deposited on a sidewall of athree-dimensional structure can demonstrate a uniform or substantiallyuniform etch rate of the SiN(B,C) film as a portion of the SiN(B,C) filmdeposited on a top surface of the structure. For example, a ratio of anetch rate of a sidewall portion of the SiN(B,C) film to an etch rate ofa top surface portion of the SiN(B,C) film can be less than about 4,including less than about 2, about 1.5. In some embodiments, the ratiois about 1.

In some embodiments, a silicon nitride film comprising boron and carboncomponents (e.g., a SiN(B,C) film) can be subjected to an annealingprocess subsequent to its formation. In some embodiments, the SiN(B,C)film can be annealed in an inert gas atmosphere (e.g., an atmospherecomprising nitrogen and/or one or more noble gases). For example, theannealing process may be performed in a nitrogen atmosphere at atemperature of about 600° C. or higher, about 800° C. or higher, or1000° C. or higher. In some embodiments, the SiN(B,C) film can beannealed at a temperature of up to about 900° C. In some embodiments,the SiN(B,C) film can be annealed in a hydrogen atmosphere, such as at atemperature of about 600° C. or higher, about 800° C. or higher, or1000° C. or higher, including up to about 900° C. In some embodiments, aboron and carbon component of the SiN(B,C) film does not diffuse out ofthe film when annealed in a nitrogen atmosphere at a temperature of upto about 900° C. In some embodiments annealing can be carried out in ahydrogen or inert gas atmosphere, for example at a temperature of about600° C. or higher, about 800° C. or higher, or 1000° C. or higher.

Examples of SiN(B,C) Films

FIG. 8A graphs the compositions (e.g., as measured by rutherfordbackscattering spectrometry (RBS)) of four films having a boron carbonprocess fraction (e.g., a percentage of the total number of cycles ofwhich are cycles of the process for introducing a boron and carboncontent into a silicon nitride SiN film) from about 0% to about 15%. Theatomic percent of silicon, nitrogen, boron, carbon and chlorine of eachof the four films are shown, with the atomic percent of silicon,nitrogen, boron and carbon shown with reference to the left verticalaxis and the atomic percent of chlorine shown with reference to theright vertical axis. Each of the four films can be formed according toone or more processes as described herein. For example, SiN films andSiN(B,C) films of varying composition can be deposited using adeposition process performed in a Pulsar®03000 chamber (e.g.,commercially available from ASM America, Inc. of Phoenix, Ariz.) using athermal ALD process for forming a silicon nitride SiN film. The thermalALD process can be performed at a temperature of about 400° C., and apressure of about 0.1 Torr to about 10 Torr, on a 300 millimeter (mm)wafer, including a silicon reactant comprising octachlorotrisilane(Si₃Cl₈, OCTS) fed into the reactor chamber with a carrier gas (e.g.,nitrogen) such that a silicon reactant pulse has a duration of about 1second and is followed by a purge step (e.g., using purge gas comprisingnitrogen) having a duration of about 5 seconds. The OCTS may be storedin a bubbler at a temperature of about 40° C. and provided into thereactor chamber from the bubbler (e.g., a mass flow rate of the OCTS maybe controlled by controlling the extent to which a valve for deliveringthe OCTS into the reactor chamber is kept open). The thermal ALD processcan include a nitrogen reactant comprising ammonia (NH₃) fed into thereactor chamber such that the nitrogen reactant pulse has duration ofabout 1 second and which is followed by a purge step (e.g., using purgegas comprising nitrogen) having a duration of about 5 seconds. The NH₃may be provided into the reactor chamber from a gas source maintained ata pressure of about 1.5 Bar (e.g., a mass flow rate of the NH₃ may becontrolled by controlling the extent to which a valve for delivering theNH₃ into the reactor chamber is kept open). The ALD process can becycled a number of times. A number of cycles of the ALD process can befollowed by a number of cycles of a pulsed thermal CVD process forintroducing boron and carbon components into the SiN film. The thermalCVD process can be performed at a temperature of about 400° C., and apressure of about 0.1 Torr to about 10 Torr, and can include a boronreactant comprising triethylboron (B(C₂H₅)₃, TEB) fed into the reactorchamber where the boron reactant pulse can have a duration of about 0.5seconds, the reactant pulse followed by a purge step (e.g., using purgegas comprising nitrogen) having a duration of about 5 seconds. Forexample, the SiN(B,C) deposition process can include a sequenceincluding a number of cycles of the ALD process followed by one to threecycles of the CVD process (e.g., to provide boron carbon processfractions of about 0% to about 15%), where the sequence can be repeateda number of times (e.g., about 50 times to about 100 times). Forexample, the sequence may be repeated 75 times.

The graphs of FIG. 8A show that a boron and a carbon content of a filmcan increase with an increase in the boron carbon process fraction. Forexample, the boron and carbon components content can increase linearlyor substantially linearly with an increase in the boron carbon processfraction. FIG. 8A shows that silicon content and nitrogen content candecrease with an increase in the boron carbon process fraction. Forexample, the silicon and/or nitrogen content can decrease linearly orsubstantially linearly with an increase in the boron carbon processfraction. FIG. 8A further shows that chlorine content can decrease withan increase in a boron carbon process fraction.

FIG. 8B graphs a film growth rate in angstroms per cycle (Å/cycle) offour films formed by fabrication processes having a boron carbon processfraction from about 0% to about 15%. A cycle, as shown in FIG. 8B, cancorrespond to a sequence including a number of cycles of a process forproviding a silicon nitride SiN film and a number of cycles of a processfor introducing boron and carbon into the SiN film (e.g., sequence 702of FIG. 7). Each of the four films can be formed according to one ormore processes as described herein, such as the processes as describedwith reference to FIG. 8A. FIG. 8B shows that a film growth rate candecrease with an increase in a boron carbon process fraction. Withoutbeing limited by any particular theory or mode of operation, boronreactants adsorbed onto a surface of a substrate may reduce the abilityof silicon reactants and/or nitrogen reactants to properly adsorb ontothe surface of the substrate (e.g., silicon reactants and/or nitrogenreactants from a subsequent silicon nitride deposition process).Increasing a boron carbon process fraction (e.g., as increased amount ofboron reactants are provided in a SiN(B,C) film fabrication process),may increasingly reduce the ability of silicon and/or nitrogen reactantsfrom subsequent silicon nitride deposition processes to adsorb onto thesubstrate surface. Further, without being limited by any particulartheory or mode of operation, the reduced ability of silicon and/ornitrogen reactants from subsequent silicon nitride deposition processesto adsorb onto the substrate surface may also result in a film havinghigher boron and carbon components content than would otherwise beexpected based on the boron carbon process fraction.

In some embodiments, a film thickness non-uniformity (e.g., a one sigma(1σ) thickness non-uniformity) may not be negatively impacted by anincreased boron carbon process fraction. In some embodiments, a filmthickness non-uniformity remain the same or substantially the same withincreased boron carbon process fraction. For example, a film thicknessnon-uniformity of a process for depositing a silicon nitride film havingboron and carbon components can be less than about 20%, including lessthan about 10%, and about 5%. In some embodiments, a film thicknessnon-uniformity can be improved with a decrease in a boron carbon processfraction up to a particular value. For example, a boron carbon processfraction of less than about 10% can provide an improved film thicknessnon-uniformity.

Referring to FIG. 9, a Fourier Transform Infrared Spectroscopy (FTIR)analysis of four films having boron carbon process fractions from about0% to about 15% is shown. Each of the four films can be formed accordingto one or more processes as described herein, such as the processes asdescribed with reference to FIG. 8A. The FTIR indicates presence ofvarious features within each film, including for example the presence ofvarious chemical bonds. For example, the FTIR analysis can show additionof features and/or changes in features of a film after being subject toa film fabrication process. Peaks corresponding to the various featuresof each film in FIG. 9 are labeled with an “0” or with an “*” toindicate an origin of the marked feature. For example, peaks in thegraph marked by an “0” indicates that the features (e.g., a hydrogenbonded to a nitrogen (N—H), a hydrogen bonded to an oxygen (O—H), ahydrogen bonded to a silicon (Si—H), a nitrogen bonded to a silicon(Si—N)) are contributed by a process for depositing the silicon nitrideSiN film. For example, peaks marked by an “*” indicate that the features(e.g., a hydrogen bonded to a carbon, a hydrogen bonded to a boron, acarbon bonded to a boron, a carbon bonded to another carbon, a boronbonded to another boron) are contributed by a process for introducing aboron and carbon components into the silicon nitride SiN film. FIG. 9shows that a process for introducing the boron and carbon into thesilicon nitride film can provide features such as a hydrogen bonded to acarbon (C—H) and/or a hydrogen bonded to a boron (B—H) (e.g., as shownin FIG. 9 between about 2500 cm⁻¹ and about 3000 cm⁻¹), and featuressuch as a carbon bonded to a boron (B—C), a boron bonded to anotherboron (B—B) and/or a carbon bonded to another carbon (C—C) (e.g., asshown in FIG. 9 between about 1000 cm⁻¹ and about 1500 cm⁻¹, such as atabout 1200 cm⁻¹). FIG. 9 shows a decrease in Si—H bonding features withan increase in the boron carbon process fraction. A reduction in Si—Hbonding features may facilitate improved SiN(B,C) film performance, forexample an improvement in an electrical property of the film. FIG. 9also shows that a peak corresponding a nitrogen bonded to a silicon(Si—N) can shift to a higher wavenumber with an increase in the boroncarbon process fraction, for example indicating a change in bondsbetween a silicon and a nitrogen.

FIG. 10 shows analysis based on X-ray reflectivity (XRR) measurements offour films having boron carbon process fractions from about 0% to about15%. Film thickness in nanometers, film density in grams per cubiccentimeter (g/cm³), and film roughness in nanometers (nm) are shown.Each of the four films can be formed according to one or more processesas described herein, such as the processes as described with referenceto FIG. 8A. FIG. 10 shows a decrease in a film density, and a slightincrease in a film roughness, with an increase in a boron carbon processfraction.

FIG. 11 graphs wet etch rates, shown in nanometers per minute (nm/min)in a dilute HF solution (e.g., 0.5 weight % HF solution) ofcorresponding films formed by processes having various boron carbonprocess fractions. The films can be formed according to one or moreprocesses as described herein, such as the processes as described withreference to FIG. 9A. As shown in FIG. 11, a wet etch rate of a siliconnitride film comprising boron and carbon components (e.g., a SiN(B,C)film) can decrease significantly with an increased boron carbon processfraction. FIG. 11 shows that film deposition processes having a boroncarbon process fraction higher than about 5% can produce SiN(B,C) filmshaving a significantly reduced wet etch rate. For example, a SiN(B,C)film having a desired wet etch rate in dilute HF may be formed by aprocess having a boron carbon process fraction of higher than about 10%(e.g., a SiN(B,C) film suitable for a spacer application).

FIGS. 12A-12D show wet etch performance of a silicon nitride filmcomprising boron and carbon components (e.g., a SiN(B,C) film) depositedon trench structures 1200 of a substrate. The film can be formedaccording to one or more processes as described herein, such as theprocesses as described with reference to FIG. 8A. FIGS. 12A and 12C showscanning electron microscopy (SEM) images of the trench structures 1200having the film 1202 on one or more surfaces of the trench structures1200 prior exposing the film 1202 to a wet etchant. For example, a wetetchant comprising a dilute hydrofluoric acid (HF) solution is used(e.g., a 0.5 weight % HF solution) for a period of time (e.g., for about2 minutes). FIGS. 12B and 12D show the film 1202 subsequent to exposureto the wet etchant. FIGS. 12B and 12D show that the film 1202 isunaffected or substantially unaffected by the wet etchant. For example,a ratio of the wet etch rate of the film 1202 to an etch rate of anunderlying thermal oxide layer (e.g., thermal silicon dioxide, TOX) canbe less than about 3:10. FIGS. 12B and 12D also show the film 1202 postwet etch providing conformal coverage of the trench structures 1200, forexample, the film 1202 not delaminating from the underlying trenchstructures and/or not demonstrating other defects.

FIGS. 13A-13D show scanning electron microscopy (SEM) images of aSiN(B,C) film on surfaces of high aspect ratio trenches 1300 subsequentto being exposed to a wet etchant (e.g., subsequent to a dip in a dilutehydrofluoric acid (HF or dHF) solution, such as a 0.5 weight % HFsolution) for a period of about 4 minutes. The film can be formedaccording to one or more processes as described herein, such as theprocesses as described with reference to FIG. 8A. FIG. 13A is a lowermagnification image, at 13 k× magnification, of the structures 1300,showing an upper portion 1302 of the trenches, a mid-section 1304 of thetrenches, and a lower section 1306 of the trenches. The upper portion1302 is shown at higher magnification, at 250 k× magnification in FIG.13B, the mid-section 1304 is shown at higher magnification, at 250 k×magnification, in FIG. 13C, and the lower-section 1306 is shown inhigher magnification, at 250 k× magnification, in FIG. 13D. As shown inFIGS. 13A-13D, the SiN(B,C) film can demonstrate excellent conformalityor step coverage of the high aspect ratio trenches 1300 subsequent tobeing exposed to the wet etchant. For example, FIGS. 13A-13D show aSiN(B,C) film having a thickness of about 20 nm formed on an upperportion 1302 of the trench structure 1300, a thickness of about 20 nmformed on a mid-section 1304 of the trench structure 1300, and athickness of about 19 nm formed on a lower portion 1306 of the trenchstructure 1300 (e.g., a conformality of about 95% or greater). A ratioof the wet etch rate of the SiN(B,C) film as shown in FIGS. 13A-13D toan etch rate of an underlying thermal oxide (e.g., thermal silicondioxide, TOX) can be less than about 1:2.

FIGS. 14A-14D show scanning electron microscopy (SEM) images of asilicon nitride film comprising boron and carbon (e.g., a SiN(B,C) film)on surfaces of high aspect ratio trenches 1400 before being exposed to awet etchant. The film can be formed according to one or more processesas described herein, such as the processes as described with referenceto FIG. 8A. FIG. 14A is a lower magnification image, at 11 k×magnification, of the trench structures 1400, with FIG. 14B showing anupper portion 1402 of the trenches 1400 at a higher magnification of 200k×, FIG. 14C showing a mid-section 1404 of the trenches 1400 at a highermagnification of 200 k×, and FIG. 14D showing a lower section 1406 ofthe trenches 1400 at a higher magnification of 200 k×. FIGS. 14A-14Dshow that the SiN(B,C) film can demonstrate excellent step coverage orconformality. For example, FIGS. 14B-14D show a SiN(B,C) film having athickness of about 23 nm formed on an upper portion 1402 of the trenchstructure 1400, a thickness of about 23 nm formed on a mid-section 1404of the trench structure 1400, and a thickness of about 24 nm formed on alower portion 1406 of the trench structure 1400 (e.g., a conformality ofabout 95% or greater).

An etch rate of the SiN(B,C) film in the wet etchant (e.g., the wetetchant having the ratio of H₂O₂:HF:H₂O of about 5:5:90 by volume) canbe about 1.1 nanometers per min (nm/min)±about 0.3 nm/min. In someembodiments, the SiN(B,C) film can be soaked in ozone (O₃) prior tobeing exposed to the wet etchant, for example to increase an etch rateof the film. An etch rate of the SiN(B,C) film soaked in ozone prior tobeing exposed to the wet etch can have a film etch rate of about 2.2nm/min±about 0.5 nm/min. In some embodiments, the etch rates can varydepending on the film composition.

A SiN(B,C) film deposited on blanket silicon wafer analyzed byrutherford backscattering spectrometry (RBS) prior to and after a dip ina 0.5 weight % HF solution for about 2 minutes show that the compositionof the as deposited film was: silicon (Si) 20 atomic %, nitrogen (N) 35atomic %, boron (B) 20 atomic %, carbon (C) 18 atomic %, oxygen (O) 6atomic %, chlorine (Cl) 1 atomic %. The composition of the filmsubsequent to being dipped in the HF solution was: Si 19 atomic %, N 30atomic %, B 25 atomic %, C19 atomic %, O 7 atomic %, Cl 1 atomic %. TheRBS analysis shows that the composition of the film may not besignificantly impacted by the HF dip process.

Although this disclosure has been provided in the context of certainembodiments and examples, it will be understood by those skilled in theart that the disclosure extends beyond the specifically describedembodiments to other alternative embodiments and/or uses of theembodiments and obvious modifications and equivalents thereof. Inaddition, while several variations of the embodiments of the disclosurehave been shown and described in detail, other modifications, which arewithin the scope of this disclosure, will be readily apparent to thoseof skill in the art based upon this disclosure. It is also contemplatedthat various combinations or sub-combinations of the specific featuresand aspects of the embodiments may be made and still fall within thescope of the disclosure. It should be understood that various featuresand aspects of the disclosed embodiments can be combined with, orsubstituted for, one another in order to form varying modes of theembodiments of the disclosure. Thus, it is intended that the scope ofthe disclosure should not be limited by the particular embodimentsdescribed above.

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the devices and methodsdisclosed herein.

What is claimed is:
 1. A method of depositing a silicon nitride thinfilm comprising boron and carbon on a substrate in a reaction spacecomprising: at least one silicon nitride cycle comprising: contactingthe substrate with a vapor-phase silicon precursor; contacting thesubstrate with a nitrogen reactant; and subsequently contacting thesubstrate with a vapor phase boron precursor, to form aSiN_(x)(B_(y),C_(z)) thin film, wherein x is from 0.5 to 3.0, wherein yis from 0.1 to 5.0, and wherein z is from 0.1 to 5.0.
 2. The method ofclaim 1, wherein the silicon nitride cycle is performed two or moretimes.
 3. The method of claim 2, wherein contacting the substrate withthe vapor phase boron precursor is performed after each silicon nitridecycle.
 4. The method of claim 2, wherein a number of silicon nitridecycles is performed at a ratio to a number of times of contacting thesubstrate with the vapor phase boron precursor.
 5. The method of claim4, wherein the ratio is from 1:1 to 100:1.
 6. The method of claim 1,wherein no plasma reactant is provided.
 7. The method of claim 1,wherein contacting the substrate with the nitrogen-containing reactantcomprises a plasma process.
 8. The method of claim 1, wherein thereaction space is part of a batch reactor.
 9. The method of claim 1,wherein the silicon nitride cycle comprises an atomic layer depositionprocess.
 10. The method of claim 9, wherein the vapor phase boronprecursor decomposes on the substrate.
 11. The method of claim 1,wherein the silicon precursor is selected from the group consisting ofsilicon halides, silicon alkylamines, and silanes.
 12. The method ofclaim 1, wherein the boron precursor is selected from the groupconsisting of boron halides, alkylborons, and boranes.
 13. The method ofclaim 1, wherein the boron precursor decomposes on the substrate. 14.The method of claim 1, wherein the silicon nitride thin film isdeposited over a three-dimensional structure.
 15. The method of claim 1,wherein the silicon nitride thin film has an etch rate of less than 0.2nm/min in dilute hydrofluoric acid solution.
 16. A method of depositinga silicon nitride thin film on a substrate in a reaction spacecomprising: a silicon nitride cycle comprising: contacting the substratewith a vapor-phase silicon precursor so that the silicon precursor isadsorbed to a surface of the substrate; removing excess siliconprecursor and reaction byproducts from the substrate surface; contactingthe adsorbed silicon precursor substrate with a nitrogen reactant; andsubsequently contacting the substrate with a vapor-phase boronprecursor, to form a SiN_(x)(B_(y),C_(z)) thin film, wherein x is from0.5 to 3.0, wherein y is from 0.1 to 5.0, and wherein z is from 0.1 to5.0, wherein the vapor-phase boron precursor decomposes on thesubstrate.
 17. The method of claim 16, wherein the silicon nitride cycleis performed two or more times.
 18. The method of claim 17, whereincontacting the substrate with the vapor phase boron precursor isperformed after each silicon nitride cycle.
 19. The method of claim 17,wherein a number of silicon nitride cycles is performed at a ratio to anumber of times of contacting the substrate with the vapor phase boronprecursor.
 20. The method of claim 19, wherein the ratio is from 1:1 to100:1.
 21. The method of claim 16, wherein a process temperature of themethod is 200° C. to 400° C.
 22. The method of claim 16, wherein thesilicon nitride thin film has a boron content of 0.1 to 50 atomic %. 23.The method of claim 16, wherein the silicon nitride thin film has acarbon content of 0.1 to 50 atomic %.
 24. The method of claim 16,wherein a boron atom in the silicon nitride thin film is bonded to acarbon atom.
 25. The method of claim 16, further comprising treating thesilicon nitride thin film in an oxygen-containing atmosphere and etchingthe treated silicon nitride thin film.
 26. The method of claim 16,wherein the silicon nitride thin film is deposited conformally over athree-dimensional structure having an aspect ratio of greater than 8:1.27. The method of claim 26, wherein the silicon nitride thin film has astep coverage of greater than 95%.
 28. The method of claim 26, wherein aratio of an etch rate of the silicon nitride thin film in a sidewall ofthe three-dimensional structure to an etch rate of the silicon nitridethin film on a top surface of the three-dimensional structure is lessthan
 4. 29. The method of claim 16, wherein the silicon nitride thinfilm has a wet etch rate ratio to thermal silicon oxide of less than 0.5in dilute hydrofluoric acid solution.
 30. The method of claim 16,wherein the silicon nitride thin film comprising boron and carbon issubstantially free of distinct layers.